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Service Training
Noise Vibration and Harshness
Self Study Programme NVH
4ABLE OF #ONTENTS #OURSE 'OALS )NTRODUCTION 4HEORY #HARACTERISTICS OF .OISE 6IBRATION AND (ARSHNESS .6( 'ENERATION OF .OISE AND 6IBRATION 3OUND AND 3OUND 7AVES !UDIBLE 2ANGE OF 3OUND .6( 4ERMINOLOGY 4YPES OF .OISE #OMPELLING &ORCE AND 6IBRATING "ODY 6IBRATION 6IBRATION 4RANSFER 0ATH 6IBRATION /RDER 4YPES OF 6IBRATION 2IDE #OMFORT
$IAGNOSIS 'ETTING 'OOD )NFORMATION FROM 3ERVICE !DVISORS 4HE &OUR 3TEPS $IAGNOSING AND 3OLVING #USTOMER #ONCERNS /THER )NFORMATION 3OURCES 0RE 2OAD 4EST )NSPECTION 2OAD 4EST 4IPS 2OAD 4ESTING
%NGINE 6IBRATIONS %NGINE 3PEED 2ELATED 6IBRATIONS 4YPES OF %NGINE 6IBRATIONS %NGINE 6IBRATION &ORMULA %NGINE !CCESSORY &ORMULA 4YPES OF %NGINE .OISE %XHAUST .OISE %NGINE &IRING &REQUENCY &ORMULA
6EHICLE 3PEED 6IBRATIONS 4IRES AND 7HEELS 4IRE 6IBRATION &ORMULAS $RIVE 3HAFT &REQUENCY &ORMULA $RIVE AND !XLE 3HAFTS $RIVELINE 6IBRATION 4RANSMISSION .OISE AND 6IBRATIONS $IFFERENTIAL /PERATION $RIVELINE 3NAP 3USPENSION #OMPONENTS 3TEERING #OMPONENTS .EW
4OOLS 3IROMETER %6! )) #HASSIS%!2 /THER 4OOLS
'LOSSARY .6( 4ERMINOLOGY
$IAGNOSTIC &LOW #HART +NOWLEDGE !SSESSMENT )MPORTANT.OTE 4HE 3ELF 3TUDY 0ROGRAM PROVIDES YOU WITH INFORMATION REGARDING DESIGNS AND FUNCTIONS 4HE 3ELF 3TUDY 0ROGRAM IS NOT A REPAIR MANUAL &OR MAINTENANCE AND REPAIR WORK ALWAYS REFER TO THE CURRENT TECHNICAL LITERATURE
Volkswagen Technical Site: http://vwts.ru http://vwts.info огромный архив документации по автомобилям Volkswagen, Skoda, Seat, Audi
I
#OURSE 'OALS
#OURSE 'OALS 4HIS COURSE WILL ENABLE YOU TO s )DENTIFY THE TERMINOLOGY USED IN DIAGNOSING .OISE 6IBRATION AND (ARSHNESS .6( CONCERNS s )DENTIFY THE DIFFERENT TYPES OF .6( s )DENTIFY THE STEPS OF THE .6( SYSTEMATIC DIAGNOSTIC APPROACH s )DENTIFY THE ROAD TEST PROCEDURES NECESSARY TO ISOLATE A NOISE OR VIBRATION s #ALCULATE .6( FREQUENCIES NECESSARY FOR COMPONENT CLASSIlCATION s )DENTIFY TEST EQUIPMENT AND TOOLS USED IN DIAGNOSING AND CORRECTING .6( CONCERNS s )DENTIFY DIAGNOSE AND SPECIFY THE COMPONENT CAUSING THE .6( CONCERN
)NTRODUCTION )NTRODUCTION 4HIS 3ELF 3TUDY 0ROGRAM FOCUSES ON VEHICLE .OISE 6IBRATION AND (ARSHNESS .6( THEIR CAUSES AND DIAGNOSTIC AND SERVICE PROCEDURES TO LOCATE AND CORRECT .6( CONCERNS -ODERN CARS AND TRUCKS USE A COMBINATION OF SYSTEMS TO PROVIDE THE DRIVER WITH THE SAFEST MOST RESPONSIVE AND COMFORTABLE VEHICLE EVER BUILT 4ODAYS DRIVER HAS COME TO EXPECT A SMOOTH AND QUIET RIDE IN ALL OPERATING ENVIRONMENTS 7HEN VEHICLE NOISE VIBRATION OR RIDE HARSHNESS EXCEEDS THE DRIVERS EXPECTATIONS IT IS UP TO THE TECHNICIAN TO CORRECT THE CAUSE OF THE CUSTOMERS CONCERN 6EHICLE COMPONENTS ARE BEING MANUFACTURED USING LIGHTER WEIGHT METALS ,IGHTER WEIGHT METALS REDUCE THE OVERALL VEHICLE WEIGHT THAT REDUCE EMISSIONS AND IMPROVE FUEL ECONOMY !S TECHNOLOGIES DEVELOP STRONGER AND MORE LIGHTWEIGHT METALS THIS TREND WILL CONTINUE ,IGHTER VEHICLE COMPONENTS DO NOT ABSORB NOISES AND VIBRATIONS AS WELL AS HEAVIER COMPONENTS 4HIS LEADS TO AN INCREASE IN .6( CONCERNS $IAGNOSING .6( CONCERNS HAS BEEN DEVELOPED INTO A LOGICAL AND ALMOST SCIENTIlC PROCEDURE 4HIS COURSE WILL PROVIDE THE !UDI TECHNICIAN WITH CONCEPTS TO HELP UNDERSTAND AND DIAGNOSE .6( CONCERNS
4HEORY #HARACTERISTICS OF .OISE 6IBRATION (ARSHNESS .OISE IS DElNED AS ANY UNPLEASANT OR UNEXPECTED SOUND CREATED BY A VIBRATING OBJECT 6IBRATION IS DElNED AS ANY OBJECTIONABLE REPETITIVE MOTION OF AN OBJECT BACK AND FORTH OR UP AND DOWN (ARSHNESS IS DElNED AS AN AGGRESSIVE SUSPENSION FEEL OR LACK OF hGIVEv IN RESPONSE TO A SINGLE INPUT
'ENERATION OF .OISE AND 6IBRATION ! VIBRATING OBJECT NORMALLY PRODUCES SOUND AND THAT SOUND MAY BE AN ANNOYING NOISE )N THE CASE WHERE A VIBRATING BODY IS THE DIRECT SOURCE OF NOISE SUCH AS COMBUSTION CAUSING THE ENGINE TO VIBRATE THE VIBRATING BODY OR SOURCE IS EASY TO lND )N OTHER CASES THE VIBRATING BODY MAY GENERATE A SMALL VIBRATION ONLY 4HIS SMALL VIBRATION MAY CAUSE A LARGER VIBRATION OR NOISE DUE TO THE VIBRATING BODYS CONTACT WITH OTHER PARTS 7HEN THIS HAPPENS ATTENTION FOCUSES ON WHERE THE LARGE VIBRATION OR NOISE OCCURS WHILE THE REAL SOURCE OFTEN ESCAPES NOTICE !N UNDERSTANDING OF NOISE AND VIBRATION GENERATION ASSISTS WITH THE TROUBLESHOOTING PROCESS 4HE DEVELOPMENT OF A SMALL NOISE INTO A LARGER NOISE BEGINS WHEN A VIBRATION SOURCE COMPELLING FORCE GENERATES A VIBRATION 2ESONANCE AMPLIlES THE VIBRATION WITH OTHER VEHICLE PARTS 4HE VIBRATING BODY SOUND GENERATING BODY THEN RECEIVES TRANSMISSION OF THE AMPLIlED VIBRATION
4HEORY 3OUNDS AND 3OUND 7AVES !UDIBLE 2ANGE OF 3OUND ! SOUND WAVES CYCLE PERIOD FREQUENCY AND AMPLITUDE DETERMINE THE PHYSICAL QUALITIES OF THE &OR SOUND TO BE HEARD THE RESULTING ACOUSTIC SOUND WAVE 4HE PHYSICAL QUALITIES OF SOUND ARE WAVE MUST HAVE A RANGE OF TO (Z WHICH IS THE AUDIBLE RANGE OF SOUND FOR HUMANS s !UDIBLE RANGE OF SOUND 7HILE MANY VEHICLE NOISES ARE CAPABLE OF BEING s 0ITCH HEARD SOME .6( NOISES ARE NOT IN THE AUDIBLE RANGE s )NTENSITY ,OW SPEED DRONING IS AN EXAMPLE OF A LOW FREQUENCY .6( CONCERN THAT MAY HAVE !LL PEOPLE HAVE DIFFERENT CAPABILITIES FOR HEARING COMPONENTS NOT IN THE AUDIBLE RANGE 4HIS SOUND 3OME PEOPLE MAY NOT HEAR SOUNDS CONDITION EXERTS PRESSURE ON THE DRIVERS THAT OTHER PEOPLE CAN HEAR +EEP THESE FACTS IN EARDRUM AND CAN BE EXTREMELY UNCOMFORTABLE MIND WHILE DIAGNOSING NOISE CONCERNS -OST /N THE OTHER END OF THE AUDIBLE RANGE OF VEHICLE CUSTOMERS BECOME TUNED INTO A NOISE AFTER NOISES ARE WIND NOISE AND BRAKE SQUEAKING HEARING IT REPETITIVELY 4HE HIGH FREQUENCIES OF THESE .6( CONCERNS PRODUCE A HIGH PITCHED NOISE THAT CAN BE 7HEN DIAGNOSING A VEHICLE IT MAY EXTREMELY ANNOYING 4HE lGURE BELOW ILLUSTRATES BE BENElCIAL TO HAVE THE CUSTOMER THE AUDIBLE RANGE OF AUTOMOTIVE NOISES REPRODUCE THE NOISE DURING A ROAD TEST
3/5.$ ,%6%L ).4%.3)49 D"
-AXIMUM !UDIBLE ,EVEL
!VERAGE !UDIBLE ,EVEL -INIMUM !UDIBLE ,EVEL
K &2%15%.#9 (Z
K
K
4HEORY .6( 4ERMINOLOGY 4HERE ARE COMMON TERMS USED WHEN DISCUSSING AN .6( CONCERN 4HE FOLLOWING TERMS AND GRAPHICS WILL HELP WHEN DISCUSSING .6( WITH OTHER PEOPLE WITH A TECHNICAL BACKGROUND
#YCLE #YCLE IS THE PATH A WAVE TRAVELS BEFORE THE WAVE BEGINS TO REPEAT THE PATH AGAIN )F AN !LTERNATING #URRENT !# SINE WAVE BEGINS A PATH AT ZERO VOLTS THE WAVE COMPLETES ONE CYCLE WHEN IT RETURNS TO ZERO VOLTS FROM A POSITIVE VOLTAGE
)N OTHER WORDS THE WAVE COMPLETES ONE CYCLE BY TRAVELING THE PATH FROM A NEGATIVE VOLTAGE TO ZERO VOLTS THEN TO A POSITIVE VOLTAGE AND THEN BACK TO ZERO VOLTS
&REQUENCY &REQUENCY IS THE NUMBER OF COMPLETE CYCLES THAT OCCUR IN ONE SECOND 3OUND AND VIBRATION WAVES ARE MEASURED IN (Z OR #YCLES 0ER 3ECOND #03 /NE (Z IS EQUAL TO ONE #03
4HE SOUND WAVE IN THE lGURE BELOW HAS A FREQUENCY OF (Z BECAUSE IT COMPLETES SEVEN #03 4HE FREQUENCY OF A SOUND OR VIBRATION CAN AID IN TROUBLESHOOTING AN .6( CONCERN
" " " " " " " !" ! " #
4HEORY 0ITCH 0ITCH IS THE PHYSICAL QUALITY OF SOUND THAT RELATES TO THE FREQUENCY OF THE WAVE )NCREASING THE FREQUENCY OF A SOUND INCREASES THE PITCH OF THE SOUND )F FREQUENCY DECREASES PITCH ALSO DECREASES
-AXIMUM
,ISTENING TO AN ACCESSORY DRIVE BELT SQUEAKING IS AN EXAMPLE OF A HIGH PITCHED HIGH FREQUENCY TYPE OF NOISE ! HIGH PITCHED HIGH FREQUENCY NOISE IS IRRITATING TO MOST PEOPLE
!MPLITUDE 0ITCH
! ROLLER BEARING THAT MAKES NOISE IS AN EXAMPLE OF A LOW PITCHED LOW FREQUENCY TYPE OF NOISE
-INIMUM
!MPLITUDE REFERS TO THE VERTICAL MEASUREMENT BETWEEN THE TOP AND THE BOTTOM OF A WAVE 4WO WAVES CAN HAVE THE SAME FREQUENCY BUT DIFFER IN AMPLITUDE !MPLITUDE IS THE QUANTITY OR AMOUNT OF ENERGY PRODUCED BY A VIBRATING COMPONENT
!-0,)45
%$!MPLITUDE
(IGH &REQUENCY (IGH 0ITCH
,OW &REQUENCY ,OW 0ITCH 4)-%
4HEORY 3OUND )NTENSITY 3OUND INTENSITY IS THE PHYSICAL QUALITY OF SOUND THAT RELATES TO THE AMOUNT AND DIRECTION OF THE mOW OF ACOUSTIC ENERGY AT A GIVEN POSITION 4HE lGURE ILLUSTRATES TWO SOUND WAVES WITH THE SAME FREQUENCY BUT DIFFERENT AMPLITUDES DIFFERENT INTENSITY LEVELS 3OUND INTENSITY IS MEASURED IN DECIBELS ! DECIBEL IS A UNIT FOR EXPRESSING RELATIVE DIFFERENCE IN POWER BETWEEN ACOUSTIC SIGNALS 3OUNDS GREATER THAN DECIBELS ARE DANGEROUS TO HUMAN HEARING
!-0,)45
%$$IFFERENCES IN PITCH THE SOURCE OF EACH SOUND OR THE PERSON WHO HEARS THE SOUND CAN CREATE THE PERCEPTION THAT TWO SOUNDS OF THE SAME INTENSITY HAVE DIFFERENT LEVELS OF LOUDNESS ,OW !MPLITUDE ,OW )NTENSITY
(IGH !MPLITUDE (IGH )NTENSITY 4)-%
4HEORY 2ESONANCE 2ESONANCE IS THE TENDENCY OF A SYSTEM TO RESPOND TO A COMPELLING FORCE OSCILLATING AT OR NEAR THE NATURAL FREQUENCY OF THE SYSTEM !LL OBJECTS HAVE NATURAL FREQUENCIES AND EXPERIENCE MAXIMUM RESPONSE AT THE POINT OF RESONANCE
4HE AMPLITUDE OF A VIBRATION IS GREATEST AT THE POINT OF RESONANCE !LTHOUGH THE VIBRATION CAN BE FELT ABOVE AND BELOW THE PROBLEM SPEED IT IS MOST PROMINENT AT THE POINT OF RESONANCE
2ESONANCE EXPLAINS WHY A TIRE VIBRATION OCCURS AT CERTAIN VEHICLE SPEEDS )F THE VEHICLEgS 4HE NATURAL FREQUENCY OF A TYPICAL AUTOMOTIVE SUSPENSION HAS A NATURAL FREQUENCY OF (Z FRONT SUSPENSION IS IN THE TO (Z RANGE 4HIS THE SUSPENSION WILL TRANSMIT OR RESONATE THE IS DESIGNED FOR RIDE AND HANDLING CONSIDERATIONS VIBRATION AT SPEEDS IN THE (Z RANGE 4HE !S SEEN IN THE lGURE THE SUSPENSIONS NATURAL VEHICLE WILL VIBRATE AT MPH MPH AND FREQUENCY IS THE SAME NO MATTER WHAT THE MPH BECAUSE THESE SPEEDS CAUSE A TIRE VEHICLE SPEED !S THE TIRE SPEED INCREASES VIBRATION TO RESONATE THROUGH THE SUSPENSION ALONG WITH THE VEHICLE SPEED THE DISTURBANCE INTO THE VEHICLE CREATED BY THE UNBALANCED TIRE INCREASES IN FREQUENCY %VENTUALLY THE FREQUENCY OF THE UNBALANCED TIRE INTERSECTS WITH THE NATURAL FREQUENCY OF THE SUSPENSION CAUSING THE SUSPENSION TO VIBRATE 4HIS INTERSECTION POINT IS CALLED THE RESONANCE
0OINT OF 2ESONANCE
(Z
3USPENSION &REQUENCY
RCE O & G
6IBRATION 3PEED
IN
LL PE
M
#O
-0(
4HEORY 4YPES OF .OISE 4HERE CAN BE MANY TYPES OF NOISE CONCERNS ON A VEHICLE 4HE CLASSIlCATION OF NOISES ASSISTS THE TECHNICIAN IN TROUBLESHOOTING AND REPAIRING THE CUSTOMERS VEHICLE
.OISE CAN BE ANNOYING TO SOME PEOPLE WHILE OTHERS lND IT ACCEPTABLE !UTOMOTIVE NOISES CAN BE AUDIBLE AT CERTAIN SPEEDS OR UNDER CERTAIN DRIVING CONDITIONS ! GEAR DRIVEN UNIT SUCH AS AN AUTOMOTIVE DRIVE AXLE PRODUCES A .OISE IS AN UNPLEASANT OR UNEXPECTED SOUND CREATED BY A VIBRATING OBJECT )NTERPRETATION PLAYS CERTAIN AMOUNT OF NOISE )N DEALING WITH THESE CONCERNS IT IS IMPORTANT TO KNOW WHAT A NORMAL A LARGE ROLE IN DElNING NOISE CHARACTERISTICS CONDITION IS AND EXPLAIN IT TO THE CUSTOMER IN 4ERMS USED TO DESCRIBE NOISE INCLUDE TERMS THEY CAN UNDERSTAND s $RONING 4RYING TO REPAIR A NORMAL VEHICLE CONDITION CAN BE FRUSTRATING $ESPITE GOOD INTENTIONS AN s "EAT ATTEMPTED REPAIR CAN ALSO BECOME A LIABILITY IF s 2OAD NOISE LEGAL ACTION IS INITIATED s "RAKE SQUEAL 4HE FREQUENCY OF NOISE VIBRATIONS IS MUCH HIGHER THAN THAT WHICH CAN ONLY BE FELT OFTEN RANGING BETWEEN AND (Z #ERTAIN NOISES CAN BE ASSOCIATED WITH THE COMPONENT SYSTEMS OF A VEHICLE SUCH AS THE ENGINE DRIVELINE AXLE BRAKES OR BODY COMPONENTS )N OTHER SITUATIONS A NOISE CAN TELEGRAPH THROUGH THE BODY OF A VEHICLE &OR EXAMPLE A CHIRPING NOISE MAY BE HEARD IN THE AREA OF THE INSTRUMENT PANEL WHEN IN FACT IT IS BEING PRODUCED BY THE REAR BRAKES 4HE SOUND HAS TRAVELED OR TELEGRAPHED THROUGH THE PARKING BRAKE CABLES &OLLOWING A SYSTEMATIC APPROACH WHEN TROUBLESHOOTING AN .6( CONCERN HELPS TO LOCATE THE CAUSE AND CORRECT THE CONDITION
4HEORY $RONING 4HE SENSATION PEOPLE EXPERIENCE WHEN DRIVING INTO A TUNNEL AT HIGH SPEED OR CLIMBING TO A HIGH ALTITUDE IS A FEELING OF EAR DISCOMFORT 4HE EAR DRUMS FEEL AS IF THEY ARE BEING FORCED IN OR OUT DUE TO SUDDEN CHANGES IN ATMOSPHERIC PRESSURE !N UNPLEASANT DRONING CAUSES A SIMILAR SENSATION DUE TO LARGE mUCTUATIONS OF AIR PRESSURE IN THE CAR ! CUSTOMER MAY REFER TO UNPLEASANT DRONING NOISES AS HUMMING NOISES 4HERE ARE THREE TYPES OF UNPLEASANT DRONING s ,OW SPEED s -IDDLE SPEED s (IGH SPEED
5NPLEASANT DRONING AT LOW AND MIDDLE SPEED DRIVING IS A LONG DURATION LOW PITCHED NOISE THAT IS NON DIRECTIONAL )T IS HARD TO HEAR AND FEELS LIKE PRESSURE IN THE EARS &EELING A SMALL AMPLITUDE VIBRATION IS COMMON WITH LOW AND MIDDLE SPEED DRONING ,OW SPEED DRONING HAS A RANGE OF UP TO MPH KPH AND HAS A FREQUENCY OF TO (Z -IDDLE SPEED DRONING HAS A RANGE OF TO MPH TO KPH WITH A FREQUENCY OF TO (Z 5NPLEASANT DRONING AT HIGH SPEED DRIVING IS A LONG DURATION NON DIRECTIONAL HUMMING NOISE THAT IS UNCOMFORTABLE TO THE EARS (IGH SPEED DRONING HAS A RANGE OF MPH KPH AND UP WITH A FREQUENCY OF TO (Z 4HE THREE CLASSIlCATIONS OF DRONING ARE SPEED AND FREQUENCY RELATED ! LOW SPEED DRONING SOUND HAS A LOWER PITCH THAN A HIGH SPEED DRONING SOUND 4HE TABLE SUMMARIZES THE SPEED AND FREQUENCY RANGES FOR THE THREE TYPES OF DRONING
3PEED AND &REQUENCY 2ANGES OF $RONING 30%%$ 2!.'%
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,OW 3PEED $RONING
5P TO MPH KPH
TO (Z
-IDDLE 3PEED $RONING
TO MPH TO KPH
TO (Z
(IGH 3PEED $RONING
MPH TO (Z KPH AND UP
4HEORY $RONING CAN OCCUR WHEN ACCELERATING DECELERATING OR DRIVING AT A CONSTANT SPEED BUT MOST OFTEN OCCURS WHEN ACCELERATING $RONING USUALLY IS APPARENT AT A SPECIlC ENGINE RPM OR VEHICLE SPEED &OR EXAMPLE THE lGURE ILLUSTRATES HOW THE NOISE LEVEL OF A VEHICLE INCREASES WITH VEHICLE SPEED !S VEHICLE SPEED REACHES A CERTAIN RANGE THE SOLID COLORED AREAS OF THE lGURE A LARGE INCREASE IN THE NOISE LEVEL OCCURS
4HE SPEED OR RPM RANGE AT WHICH UNPLEASANT DRONING OCCURS IS RELATIVELY NARROW 7HEN DRONING OCCURS AT A SPECIlC VEHICLE SPEED THE RANGE IS GENERALLY WITHIN MPH KPH OF THAT SPEED 7HEN DRONING OCCURS AT A SPECIlC ENGINE RPM THE TECHNICIAN SHOULD CHANGE VEHICLE SPEED VERY SLOWLY #HANGING VEHICLE SPEED QUICKLY WILL MAKE IT DIFlCULT TO CHECK THE DRONING BECAUSE RPM WILL PASS THROUGH THE SPECIlC RANGE TOO QUICKLY $RONING IS USUALLY GENERATED BY MORE THAN ONE COMPONENT )N MOST CASES IT IS NECESSARY TO ELIMINATE ALL THE CAUSES IN ORDER TO REMOVE THE DRONING NOISE &OR EXAMPLE UNPLEASANT DRONING CAN OCCUR WHEN ENGINE AND DRIVELINE VIBRATIONS ARE TRANSMITTED TO THE BODY PANELS CAUSING THEM TO RESONATE !IR CLEANER AIR INTAKE AND EXHAUST NOISES CAN COMBINE AND CAUSE DRONING IN THE PASSENGER COMPARTMENT /THER ITEMS THAT ARE SOMETIMES RESPONSIBLE FOR UNPLEASANT DRONING INCLUDE s "ENDING RESONANCE OF EXHAUST PIPES
s 2ESONANCE OF AUXILIARY EQUIPMENT s "ENDING RESONANCE OF PROPELLER SHAFT s 2ESONANCE OF SUSPENSION LINKS
s 4RANSMISSION OF ENGINE VIBRATION
s 4RANSMISSION OF EXHAUST NOISE s 4RANSMISSION OF INTAKE AIR NOISE
4HE BENDING RESONANCE IS A NORMAL OCCURRENCE FOR STRAIGHT TUBES AND PIPES AND EXHAUST AND DRIVE SHAFTS 4HESE COMPONENTS DEFORM RESONATE AT KNOWN FREQUENCIES %NGINEERS DESIGN COMPONENTS SO THAT THE BENDING RESONANCE WILL NOT OCCUR DURING THE NORMAL OPERATION OF THE VEHICLE
4HEORY "EAT &OR BEAT SOUNDS TO DEVELOP THERE MUST BE TWO SOUND SOURCES &OR EXAMPLE STRIKING A TUNING FORK PRODUCES A PURE TONE OF A CERTAIN FREQUENCY PITCH )F A SECOND TUNING FORK WITH A VERY DIFFERENT PITCH IS STRUCK EACH TONE IS DISTINGUISHABLE FROM ONE ANOTHER (OWEVER IF THE PITCHES OF THE TUNING FORKS ARE SIMILAR THE TWO TONES PRODUCE A BEAT SOUND WITH A PITCH THAT OCCURS IN CYCLES AT THE DIFFERENCE OF THE TWO FREQUENCIES )F THE PITCHES OF THE TWO SOUNDS ARE THE SAME OR ONLY SLIGHTLY DIFFERENT THEY ARE INDISTINGUISHABLE AND ARE PERCEIVED AS ONE SOUND 4HE lGURE ILLUSTRATES TWO TUNING FORKS PRODUCING SOUND WAVES WITH TROUGHS AND PEAKS 4HE TWO WAVES HAVE SLIGHTLY DIFFERENT FREQUENCIES 4HE SOUND LEVEL BECOMES HIGHER WHEN THEIR PEAKS OCCUR AT THE SAME TIME 4HE SOUND LEVEL DROPS WHEN A PEAK OF ONE WAVE OCCURS AT THE SAME TIME AS THE TROUGH OF THE OTHER WAVE 7HEN THE TWO WAVES COMBINE THEY PRODUCE A BEAT SOUND IN WHICH LOUDNESS CHANGES PERIODICALLY
4HE SENSATION OF A BEAT SOUND IS MOST NOTICEABLE WHEN THE FREQUENCY DIFFERENCE IS TO (Z )F THE TWO FREQUENCIES ARE CLOSER THEIR TONES ARE INDISTINGUISHABLE AND ARE SENSED AS THE SAME SOUND )F THE TWO FREQUENCIES ARE GREATER THAN (Z APART EACH TONE IS DISTINGUISHABLE FROM ONE ANOTHER "EAT SOUNDS CAN RESULT FROM A COMBINATION OF MANY TYPES OF VIBRATIONS #OMMON COMBINATIONS THAT RESULT IN BEAT SOUNDS INCLUDE s %NGINE AND AIR CONDITIONING COMPRESSOR s %NGINE AND POWER STEERING HYDRAULIC PUMP OR OTHER ACCESSORIES s %NGINE AND VIBRATIONS OF THE DRIVE SHAFT s 4IRE NON UNIFORMITY s 4IRE AND DRIVE SHAFT VIBRATIONS
! (Z
" (Z
#
3OUND 7AVES # ARE THE SUM OF 3OUND 7AVES ! AND " 4HE mUCTUATION IN -AGNITUDE IS 0HASING OR "EATING
4HEORY 2OAD .OISE 4HE SOUNDS THAT OCCUR WHILE DRIVING ON GRAVEL OR ROUGHLY PAVED ROADS IS AN EXAMPLE OF ROAD NOISE 4HIS TYPE OF NOISE IS CONTINUOUS AND HAS A CONSTANT CHARACTER 2OAD NOISE CAN OCCUR AT ALL VEHICLE SPEEDS OR WHEN THE VEHICLE IS COASTING AND HAS A FREQUENCY RANGE OF TO (Z ! VERY lNE VIBRATION ALSO MAY BE NOTICEABLE 2OAD ROUGHNESS AND TIRES ARE MAJOR SOURCES OF NOISE AND VIBRATION THAT OCCUR DURING DRIVING 3INCE THE SOURCE OF ROAD NOISE IS IRREGULAR ROAD SURFACES DIFFERENT TYPES OF TIRES CAN INmUENCE THE AMOUNT OF ROAD NOISE 4HE IMPACT FORCE FROM ROAD SURFACES TRANSMITS TO THE TIRES CAUSING THEM TO VIBRATE 4HIS VIBRATION IN TURN TRANSMITS TO THE SUSPENSION AND BODY 4HE RESONANCE CHARACTERISTIC OF THE PASSENGER COMPARTMENT AMPLIlES THE VIBRATION AND GENERATES ANNOYING ROAD NOISE
4HEORY "RAKE 3QUEAL 4HE MOST COMMON BRAKE SYSTEM .6( CONCERN IS BRAKE SQUEAL "RAKE SQUEAL IS A HIGH PITCHED NOISE )F BRAKE SQUEAL ONLY APPEARS WHEN THE VEHICLE IS lRST PUT INTO OPERATION IT MAY BE DUE TO MOISTURE ON THE BRAKE LININGS "RAKE SQUEAL ALSO CAN OCCUR WHEN FRICTION IS CREATED BETWEEN BRAKE COMPONENTS DURING BRAKING 7ORN OR DAMAGED BRAKE COMPONENTS CAN PRODUCE A VIBRATION RESULTING IN BRAKE SQUEAL 4HIS HIGH FREQUENCY NOISE CAN OCCUR UNDER DIFFERENT BRAKE PEDAL PRESSURES VEHICLE SPEEDS AND BRAKE TEMPERATURES $RUM BRAKES USUALLY EMIT A LOWER PITCH NOISE THAT GETS LOUDER WITH INCREASED BRAKE PEDAL PRESSURE $ISC BRAKE NOISE IS GENERALLY A HIGH PITCHED SQUEAL THAT OCCURS UNDER LIGHT PEDAL PRESSURE 4HE MAJOR VIBRATION SOURCES OF BRAKE SQUEAL ARE s 7ORN BRAKE SHOES s .ON UNIFORM THICKNESS OF BRAKE DISC OR DRUMS s %XCESSIVE RUNOUT s $AMAGE OR CONTAMINATION OF FRICTION SURFACES "ECAUSE OF THE COMPLEX NATURE OF BRAKES AND THE MANY DIFFERENT PARTS FOUND IN THEM THE BEST WAY TO CORRECT BRAKE SQUEAL IS TO FOLLOW SERVICE PROCEDURES $URING BRAKE SERVICE ALWAYS THOROUGHLY CLEAN ANY FRICTION SURFACE BEFORE REASSEMBLING THE BRAKE ! WIDE VARIETY OF COATING MATERIALS USED ON BRAKE BACKING SURFACES AND THE INSTALLATION OF SHIMS AND CLIPS CAN HELP ELIMINATE BRAKE SQUEAL .6( CONCERNS
4HEORY #OMPELLING &ORCE AND 6IBRATING "ODY 6IBRATIONS OCCUR WHEN THERE IS A COMPELLING FORCE OR EXCITING FORCE ACTING UPON AN OBJECT THAT CAUSES THE BODY TO VIBRATE ,OCATING THE COMPELLING FORCE THE SOURCE OF THE VIBRATION CAN ASSIST IN ELIMINATING AN .6( CONCERN 4HE MAJOR COMPONENT GROUPS THAT PRODUCE COMPELLING FORCES ARE s 4IRE AND WHEEL s $RIVELINE s %NGINE AND TORQUE CONVERTER
6IBRATION 6IBRATION IS THE REPETITIVE MOTION OF AN OBJECT BACK AND FORTH OR UP AND DOWN 4HIS MOTION IS A FUNCTION OF TIME AND IS MEASURABLE IN (Z 6IBRATION CAN BE DESCRIBED IN MANY WAYS WHICH INCLUDE s 3HAKE s 3HIMMY s 3HUDDER 6IBRATIONS CAN BE CONSTANT OR VARIABLE AND OCCUR DURING A PORTION OF THE TOTAL OPERATING SPEED RANGE 6IBRATIONS USUALLY ARE CAUSED BY SOME ROTATING COMPONENT OR COMPONENTS OR SOMETIMES BY THE COMBUSTION OF THE AIRFUEL MIXTURE IN THE INDIVIDUAL ENGINE CYLINDERS
5NDER NORMAL CIRCUMSTANCES A ROTATING COMPONENT DOES NOT PRODUCE A NOTICEABLE VIBRATION (OWEVER IF THE COMPONENT HAS IMPROPER WEIGHT DISTRIBUTION IMBALANCE OR IS ROTATING IN AN ECCENTRIC PATTERN OUT OF ROUND OR BENT THEN A NOTICEABLE VIBRATION MAY BE PRODUCED )F THE CHARACTERISTICS OF THE VIBRATION CAN BE MEASURED THE INFORMATION ABOUT THE VIBRATION CAN BE USED TO MATCH IT WITH COMPONENTS THAT ARE THE LIKELY CAUSE 4HERE ARE MANY TYPES OF VIBRATION PROBLEMS ON A VEHICLE 4HE CLASSIlCATION OF VIBRATIONS ASSISTS THE TECHNICIAN IN TROUBLESHOOTING AND REPAIRING THE CUSTOMER CONCERN
6IBRATION 4RANSFER 0ATH 6IBRATIONS TRAVEL THROUGH A VEHICLES STRUCTURE SIMILAR TO THE WAY RADIO WAVES TRAVEL THROUGH AIR 6IBRATIONS ARE OFTEN NOTICED IN A COMPONENT FAR REMOVED FROM WHERE THEY ARE GENERATED 4RANSMISSION OF A VIBRATION TO OTHER COMPONENTS IS CALLED hTELEGRAPHINGv &OR EXAMPLE AN OUT OF BALANCE FRONT TIRE AND WHEEL ASSEMBLY MAY RESULT IN A NOTICEABLE STEERING WHEEL SHAKE )N THIS CASE THE WHEEL AND TIRE ASSEMBLY IS THE ORIGINATOR OF THE VIBRATION THE SUSPENSION IS THE CONDUCTOR AND THE STEERING WHEEL IS THE REACTOR
4HEORY 6IBRATION /RDER /RDER IS THE NUMBER OF DISTURBANCES CREATED IN ONE REVOLUTION OF A COMPONENT ! SINGLE HIGH SPOT ON A TIRE CAUSES ONE DISTURBANCE PER REVOLUTION AND IS CALLED A lRST ORDER DISTURBANCE )F THE WHEEL ROTATES TIMES PER SECOND THERE ARE DISTURBANCES PER SECOND 4HIS CREATES A lRST ORDER DISTURBANCE OF (Z )F THE TIRE DEVELOPED A SECOND HIGH SPOT A SECOND ORDER DISTURBANCE WOULD RESULT 4HE WHEEL ROTATING TIMES PER SECOND PRODUCES DISTURBANCES PER SECOND 4HIS CREATES A SECOND ORDER DISTURBANCE OF (Z 4HREE HIGH SPOTS CREATE A THIRD ORDER DISTURBANCE AND FOUR HIGH SPOTS CREATE A FOURTH ORDER DISTURBANCE (IGHER ORDER DISTURBANCES CONTINUE TO PROGRESS IN THIS WAY
4HE VIBRATION ORDER CAN AID THE TECHNICIAN WHILE TROUBLESHOOTING &OR EXAMPLE A VEHICLE HAS AN .6( CONCERN THAT IS PRODUCING A VIBRATION AT (Z !FTER CALCULATING DRIVE SHAFT FREQUENCY IT IS DETERMINED THE DRIVE SHAFT HAS A FREQUENCY OF (Z 4HE SECOND ORDER FREQUENCY OF THE DRIVE SHAFT IS (Z 4HIS MATCHES THE FREQUENCY OF THE .6( CONCERN "Y DETERMINING THAT THE .6( CONCERN IS A POSSIBLE SECOND ORDER VIBRATION YOU WOULD LOOK AT COMPONENTS THAT COULD CAUSE A VIBRATION OF THIS TYPE 5NIVERSAL JOINTS WOULD BE A GOOD COMPONENT TO CHECK BECAUSE IT IS POSSIBLE THEY COULD PRODUCE TWO DISTURBANCES WITH EACH REVOLUTION OF THE DRIVE SHAFT ! MISSING DRIVE SHAFT WEIGHT COULD BE ELIMINATED FROM THE LIST OF POSSIBILITIES BECAUSE THIS SITUATION WOULD PRODUCE A VIBRATION OF THE lRST ORDER
&IRST ORDER 6IBRATION
3ECOND ORDER 6IBRATION
4HEORY 6IBRATION /RDER %XAMPLES (ALF ORDER VIBRATION
3ECOND ORDER VIBRATION
(ALF ORDER VIBRATION IS CREATED WHEN ANY COMPONENT THAT ROTATES AT HALF THE CRANKSHAFT SPEED IS OUT OF BALANCE OR HAS EXCESSIVE RUNOUT !N EXAMPLE OF THIS IS CAMSHAFT IMBALANCE "ALANCING THE COMPONENT OR CORRECTING THE RUNOUT MAY BRING THE VIBRATION TO AN ACCEPTABLE LEVEL
3ECOND ORDER VIBRATION IS CAUSED BY THE UP AND DOWN MOTION OF THE PISTONS 4HIS REVERSAL OF MASS AND MOTION CREATES A NATURAL VIBRATION
&IRST ORDER VIBRATION &IRST ORDER VIBRATION IS CREATED WHEN ANY COMPONENT THAT ROTATES AT CRANKSHAFT SPEED IS OUT OF BALANCE OR HAS EXCESSIVE RUNOUT %XAMPLES ARE mYWHEEL OR TORQUE CONVERTER IMBALANCE AND CYLINDER TO CYLINDER MASS DIFFERENCES )N RARE CASES THE CRANKSHAFT ITSELF MAY BE IMBALANCED "ALANCING THE COMPONENT OR CORRECTING THE RUNOUT MAY BRING THE VIBRATION TO AN ACCEPTABLE LEVEL
3YMPTOMS OF ENGINE IMBALANCE INCLUDE s ! LOW SPEED SHAKE FELT BETWEEN AND 2EVOLUTIONS 0ER -INUTE RPM THAT HAS A FREQUENCY OF TO (Z s ! ROUGHNESS SOMETIMES FELT AND HEARD BETWEEN TO RPM AT A FREQUENCY OF TO (Z &IRST AND SECOND ORDER ENGINE VIBRATIONS USUALLY ARE DETECTED DURING THE NEUTRAL RUN UP TEST
4HIRD ORDER VIBRATION ! THIRD ORDER VIBRATION IS CAUSED BY ANY COMPONENT THAT HAS THREE HEAVY SPOTS
4HEORY 4YPES OF 6IBRATION 6IBRATIONS IN A VEHICLE CAN BE ANY ONE OF THE FOLLOWING TYPES s 3HAKE s 3HIMMY s "RAKE 6IBRATION3HUDDER
3HAKE 6IBRATIONS AT THE STEERING WHEEL OR SEAT OR AN ANNOYING VIBRATION AT THE mOOR ARE INDICATORS OF hSHAKEv 3HAKE GENERALLY HAS A FREQUENCY OF TO (Z 4HERE ARE TWO TYPES OF SHAKE s 6ERTICAL UP AND DOWN s ,ATERAL SIDE TO SIDE 6ERTICAL SHAKE IS SEVERE VERTICAL VIBRATION OF THE BODY SEATS AND STEERING WHEEL ! TREMBLING ENGINE HOOD OR REARVIEW MIRROR ALSO CAN BE A VERTICAL SHAKE SYMPTOM ,ATERAL SHAKE IS SIDE TO SIDE VIBRATION OF THE BODY SEATS AND STEERING WHEEL ! TREMBLING VIBRATION IN THE DRIVERS WAIST OR HIPS MAY BE A SYMPTOM OF A LATERAL SHAKE 4HE MAJOR VIBRATION SOURCES OF VERTICAL AND LATERAL SHAKE ARE s 2OUGHNESS OF ROAD s 4IRE IMBALANCE s .ON UNIFORM TIRES s "ENT OR OUT OF ROUND WHEELS s $RIVELINE s %NGINE
4HEORY 3HIMMY 6IBRATION THAT CAUSES THE STEERING WHEEL TO OSCILLATE IS KNOWN AS hSHIMMYv 4HE BODY OF THE VEHICLE ALSO MAY VIBRATE LATERALLY 3HIMMY GENERALLY HAS A FREQUENCY OF TO (Z 4HERE ARE TWO TYPES OF SHIMMY s (IGH SPEED SHIMMY s ,OW SPEED SHIMMY (IGH SPEED SHIMMY OCCURS WHEN DRIVING ON SMOOTH ROADS AT HIGH SPEEDS (IGH SPEED SHIMMY TYPICALLY HAS A LIMITED SPEED RANGE IN WHICH SYMPTOMS ARE NOTICEABLE ,OW SPEED SHIMMY OCCURS WHEN THE STEERING WHEEL BEGINS TO VIBRATE AS THE VEHICLE IS DRIVEN ACROSS A BUMP AT LOW SPEEDS
4HE MAJOR VIBRATION SOURCES OF HIGH SPEED AND LOW SPEED SHIMMY ARE s 2OUGHNESS OF ROAD s 4IRE IMBALANCE s .ON UNIFORM TIRES s "ENT OR OUT OF ROUND WHEELS &OR EXAMPLE A TIRE WITH EXCESSIVE RUNOUT OUT OF BALANCE OR OUT OF ROUND MAY CAUSE HIGH OR LOW SPEED SHIMMY 4HIS IS BECAUSE THE TIRE FAULT GENERATES A VIBRATION AT A PARTICULAR FREQUENCY 7HEN THE VIBRATION OF THE TIRE REACHES THE NATURAL FREQUENCY OF THE VEHICLES FRONT UNSPRUNG COMPONENTS SUCH AS THE FRONT AXLE TIRES AND WHEELS THEY START TO VIBRATE 7HEN THE FREQUENCY OF THE FRONT UNSPRUNG COMPONENTS MATCHES THE NATURAL FREQUENCY OF THE STEERING SYSTEM RESONANCE OCCURS 4HIS RESONANCE CAUSES THE STEERING WHEEL TO VIBRATE HEAVILY IN THE TURNING DIRECTION
4HEORY "RAKE 6IBRATION3HUDDER "RAKE VIBRATIONSHUDDER IS TRANSMITTED THROUGH THE BRAKE HYDRAULIC LINES TO THE SUSPENSION SYSTEM STEERING SYSTEM AND THE BRAKE PEDAL "RAKE PEDAL PULSATION IS GENERATED WHEN APPLYING A BRAKE WITH A NON UNIFORM DIAMETER DRUM OR A DISC BRAKE WITH NON UNIFORM BRAKE DISC THICKNESS "RAKE SHUDDER CAUSES THE INSTRUMENT PANEL STEERING WHEEL AND SOMETIMES THE ENTIRE BODY TO VIBRATE VERTICALLY AND BACK AND FORTH DURING BRAKING )T ALSO MAY RESULT IN BRAKE PEDAL PULSATION RELATED TO WHEEL ROTATION AND CAN OCCUR DURING ANY BRAKING CONDITION OR VEHICLE SPEED .ORMALLY BRAKE SHUDDER HAS A PEAK AT TO MPH TO KPH AND HAS A FREQUENCY OF TO (Z #ERTAIN OPERATING CONDITIONS CAN AFFECT THE CAUSE OF THESE VIBRATIONS 4HESE INCLUDE s %XTENDED PERIODS WHERE THE VEHICLE IS NOT IN OPERATION s "RAKE DISC SURFACE IRREGULARITIES DUE TO FOREIGN AGENTS OIL OR GREASE ANTIFREEZE ETC s $EFORMATION OF BRAKE DRUM DUE TO POOR INSTALLATION
)F THE DISC ROTOR HAS EXCESSIVE THICKNESS VARIATION FRICTION FORCE ON THE BRAKING SURFACE VARIES DURING BRAKE APPLICATION 4HE CHANGE IN THE BRAKING FORCE GENERATES A VIBRATION AT A CERTAIN FREQUENCY 4HIS VIBRATION IS TRANSMITTED TO THE SUSPENSION STEERING AND BRAKE PEDAL 4HE VIBRATION CAN ALSO TRANSMIT TO THE BODY CAUSING IT TO RESONATE 4HE ROOT CAUSE OF DISC BRAKE VIBRATIONSHUDDER CONCERNS IS THICKNESS VARIATION 4HICKNESS VARIATION CAN BE CAUSED BY A ROTOR THAT HAS LATERAL RUNOUT ,ATERAL RUNOUT CAN BE CAUSED BY IMPROPER WHEEL TIGHTENING PROCEDURES AND TORQUE VALUES AS WELL AS HUB RUNOUT !S THE ROTOR WOBBLES LATERAL RUNOUT CONTACT IS MADE WITH THE BRAKE PADS !S SECTIONS OF THE ROTOR MAKE CONTACT WITH THE PADS SMALL AMOUNTS OF METAL WEAR FROM THE ROTOR SURFACE 4HIS CONTINUES UNTIL ENOUGH METAL IS WORN IN SECTIONS TO CAUSE THICKNESS VARIATION 4HIS IS WHY IMPROPER WHEEL TIGHTENING PROCEDURES OFTEN TAKE WEEKS OR MONTHS TO PRODUCE BRAKE VIBRATIONS 4HE SAME IS TRUE FOR HUB RUNOUT 2ESURFACING OR REPLACING ROTORS WHEN THE HUB HAS LATERAL RUNOUT IS USUALLY A SHORT TERM REPAIR !LWAYS FOLLOW SERVICE INFORMATION FOR PROPER WHEEL TIGHTENING PROCEDURES AND TORQUE VALUES #HECK THE HUB FOR LATERAL RUNOUT WHEN RESURFACING OR REPLACING ROTORS FOR A BRAKE VIBRATION )F THE VIBRATION OR NOISE IS CAUSED BY THE BRAKE SYSTEM REFER TO SERVICE MANUAL INFORMATION FOR THE VEHICLE 0ROCEDURES TO CHECK DRUMS AND ROTORS FOR OUT OF ROUND THICKNESS VARIATION AND LATERAL RUNOUT ARE COVERED IN THE SERVICE INFORMATION /VERTIGHTENING WHEEL BOLTS SUCH AS WITH AN IMPACT WRENCH OFTEN CAUSES ROTOR WARPAGE "E SURE WHEEL NUTS ARE CORRECTLY TORQUED
4HEORY 2IDE #OMFORT 2IDE COMFORT PLAYS A LARGE PART IN A CUSTOMERS SATISFACTION WITH THEIR VEHICLE !VOIDING ABNORMAL VIBRATIONS ENSURES A QUALITY RIDE COMFORT LEVEL .ORMAL VEHICLE VIBRATIONS ARE A RESULT OF ROAD ROUGHNESS $URING NORMAL OPERATION THE VEHICLE EXPERIENCES VIBRATION BETWEEN THE SPRUNG COMPONENTS BODY AND SUSPENSION AND THE UNSPRUNG COMPONENTS AXLES TIRES AND WHEELS 4HIS IS AN ACCEPTABLE CONDITION UNLESS THE SPRUNG OR UNSPRUNG COMPONENTS BECOME DEFECTIVE WORN OR DAMAGED 7HEN UNSPRUNG COMPONENTS RESONATE WITH THE SPRUNG COMPONENTS THE RESULT IS POOR RIDE COMFORT 2IDE COMFORT VIBRATIONS MAY CAUSE THE VEHICLE TO ROLL PITCH AND BOUNCE WHICH MAY CAUSE A CUSTOMER CONCERN 0OOR RIDE COMFORT CAN BE MINIMIZED BY ENSURING SUSPENSION AND STEERING COMPONENTS ARE NOT DAMAGED OR WORN
4HEORY (ARSHNESS (ARSHNESS RESULTS WHEN THE VEHICLE IS UNABLE TO ABSORB VIBRATIONS PRODUCED BY ROAD CONDITIONS 4HE CAUSES MAY BE DUE TO DETERIORATION OF VEHICLE COMPONENTS DAMAGE OR MODIlCATION OF THE ORIGINAL EQUIPMENT )N MOST CASES HARSHNESS IS RELATED TO CHASSIS COMPONENTS 7HEN DIAGNOSING A HARSHNESS CONCERN PAY CLOSE ATTENTION TO INTERIOR NOISE LEVELS IN THE VEHICLE -ANY HARSHNESS CONDITIONS ARE DUE TO A COMPONENT THAT IS NOT ALLOWED TO MOVE WITHIN ITS NORMAL TRAVEL OR ONE THAT HAS LOST ITS ISOLATING GROMMETS OR BUSHINGS 4HIS MAKES ENGINE MOUNTS SUBFRAME MOUNTS BUSHINGS AND SUSPENSION COMPONENTS PRIME SUSPECTS IN THE DIAGNOSTIC PROCEDURE
-ANY CUSTOMERS USE THE WORD hHARSHNESSv TO DESCRIBE RIDE COMFORT CONCERNS (ARSHNESS HAS BECOME A UNIVERSAL TERM WHEN DEALING WITH .6( CONCERNS ON A VEHICLE &OR THE PURPOSE OF THIS COURSE HARSHNESS IS AN AGGRESSIVE SUSPENSION FEEL OR LACK OF hGIVEv IN RESPONSE TO A SINGLE INPUT )T CAN BE ASSOCIATED WITH AN ABRUPT THUMPING NOISE AS WELL AS AN AGGRESSIVE FEEL
/VERSIZED TIRES HEAVY DUTY SPRINGS AND SHOCKS OR OTHER VEHICLE MODIlCATIONS ALSO MUST BE CONSIDERED 3OME AFTERMARKET TIRES EVEN WHEN THEY ARE THE CORRECT SIZE MAY PRODUCE CHANGES IN THE VEHICLE THAT WILL GENERATE OWNER CONCERNS
(ARSHNESS OCCURS WHEN A VEHICLE VIBRATES FROM MOVING ACROSS ROAD JOINTS PROJECTIONS STEPPED DIFFERENCES OR DEPRESSIONS ON PAVED ROADS $RIVING ON THE EXPRESSWAY INCREASES THE PITCH OF THE THUMPING SOUND 4HE IMPACT FORCE FROM THE ROAD SURFACE CAUSES THE TIRES TO VIBRATE 4HE TIRES TRANSMIT THE VIBRATION THROUGH THE SUSPENSION SYSTEM TO THE CAR BODY (ARSHNESS HAS A FREQUENCY OF TO (Z
4HEORY 6IBRATIONS 6IBRATIONS ARE NOTICEABLE AT THE STEERING WHEEL SEATS AND mOOR 4HE LEVEL AND INTENSITY OF THE VIBRATION CHANGES WITH THE SUSPENSION TYPE AND THE BUSHINGS USED ,ONGITUDINAL IMPACT FORCES ARE TRANSMITTED TO THE LOWER ARMS WHERE SUSPENSION BUSHINGS DAMPEN THE VIBRATION 4HE DAMPENED VIBRATION THEN TRANSMITS THROUGH THE SUSPENSION CROSSMEMBER AND STRUT INSULATORS TO THE BODY 4HE RIGIDITY OF THE BUSHINGS AND INSULATORS IN THE VIBRATION TRANSMISSION PATH HAS A LARGE INmUENCE ON HARSHNESS 4HE USE OF LOW RIGIDITY BUSHINGS AND INSULATORS TO PROVIDE GREATER FORE AFT SUSPENSION COMPLIANCE SOFTENS THE IMPACT FORCE EFFECTIVELY BUT RESULTS IN LESS RESPONSIVE STEERING !LONG WITH SUSPENSION SYSTEM DESIGNS TIRE CHARACTERISTICS INmUENCE THE AMOUNT OF HARSHNESS 7HEN TIRES EXPERIENCE AN IMPACT FORCE FROM A PAVEMENT JOINT THEY DEFORM TO CUSHION THE REST OF THE VEHICLE 4HE TIRES ABSORB THE FORCE TO SOME EXTENT AND ARE AN IMPORTANT FACTOR WHEN DEALING WITH HARSHNESS !T THE SAME TIME THE DEFORMATION TRANSMITS VIBRATION TO OTHER PORTIONS OF THE TIRES 4HIS CAUSES THE TIRES TO UNDERGO COMPLICATED RESILIENT VIBRATIONS ! TIRE THAT CAN ABSORB VIBRATIONS FROM IMPACT IS EFlCIENT IN CONTROLLING THE PROBLEM OF HARSHNESS
)T IS EXTREMELY DIFlCULT FOR A TIRE TO ABSORB HARSHNESS VIBRATIONS COMPLETELY 4HESE VIBRATIONS INVOLVE NOT ONLY TIRE TYPE BUT ALSO INmATION PRESSURE 4HE TECHNICIAN SHOULD ALWAYS ENSURE PROPER TIRE INmATION PRESSURE WHEN TROUBLESHOOTING A HARSHNESS CONCERN 'ENERALLY A SOFT TIRE WITH ENVELOPING CHARACTERISTICS PERFORMS WELL IN PREVENTING HARSHNESS 2ADIAL TIRES HAVE RIGID TREADS AND ARE LOW IN ENVELOPING CHARACTERISTICS 4HEY TEND TO CAUSE HARSHNESS PARTICULARLY AT TO MPH TO KPH
$IAGNOSIS 'ETTING 'OOD )NFORMATION FROM 3ERVICE !DVISORS 4O PROPERLY DIAGNOSE AND REPAIR AN .6( CONCERN THE CONCERN WILL NEED TO BE DUPLICATED DURING A ROAD TEST 4HE SERVICE ADVISORS ARE A GOOD SOURCE FOR THE SYMPTOMS AND FACTS SURROUNDING THE CONCERN 0ROPER QUESTIONING OF THE CUSTOMER WILL USUALLY PROVIDE THE INFORMATION NECESSARY TO DUPLICATE THE CONCERN )F THE CUSTOMER IS LEAVING THE VEHICLE AND WILL BE UNAVAILABLE FOR A ROAD TEST LATER IN THE DAY THEN IT IS ADVISABLE THAT THE SERVICE ADVISOR OR TECHNICIAN ROAD TEST WITH THE CUSTOMER BEFOREHAND TO EXPERIENCE THE SYMPTOMS AND FACTS OF THE .6( CONCERN 4HE &OUR 3TEPS &OCUS THE DISCUSSION WITH THE CUSTOMER ON THE SYMPTOM DESCRIPTION
$IAGNOSING AND 3OLVING #USTOMER #ONCERNS $ESCRIBE THE CONCERN s ,IST KNOWN SYMPTOMS s !VOID OPINIONS OR DISGUISED SOLUTIONS 6ERIFY AND ANALYZE s 4RY TO DUPLICATE THE CONCERN s ,IST POSSIBLE CAUSES ,OCATE THE CONCERN s 3ELECT THE PROBABLE CAUSES s 0RIORITIZE TASKS s )DENTIFY THE CONCERN 2EPAIR THE CONCERN s $ETERMINE THE SPECIlC CAUSE
!SK QUESTIONS THAT CLARIFY WHAT WHEN WHERE AND HOW OFTEN 3UMMARIZE YOUR UNDERSTANDING AND GET AGREEMENT FROM THE CUSTOMER 5SE OPEN ENDED QUESTIONS TO PROMPT FOR SPECIlCS %XPLAIN WHAT YOU WILL DO TO PROCEED AND GET ACKNOWLEDGEMENT FROM THE CUSTOMER
s 0ERFORM THE REPAIR #ONDUCT A QUALITY CHECK s 2ECHECK FOR PROPER OPERATION AND REASSEMBLY s #HECK FOR CLEANLINESS AND APPEARANCE /THER )NFORMATION 3OURCES s !UDI %LECTRONIC 3ERVICE )NFORMATION 3YSTEM !%3)3 n 4ECHNICAL "ULLETINS s /THER TECHNICIANS s (ELPLINE s +NOWN GOOD VEHICLE s 4HIS TRAINING MANUAL s 4HE '30 6IBRATION #ONTROL 3YSTEM /PERATION )NSTRUCTIONS
$IAGNOSIS 0RE 2OAD 4EST )NSPECTION
2OAD 4EST 4IPS
"EGIN CHECKING THE VEHICLE WITH A VISUAL INSPECTION "E SURE TO CAREFULLY INSPECT THE TIRES UNLESS THE .6( CONCERN ONLY OCCURS AT A STANDSTILL 0RIOR TO THE ROAD TEST INSPECT THE FOLLOWING
/BSERVE THE FOLLOWING GUIDELINES WHEN PREPARING FOR THE ROAD TEST
s 4IRES 0RESSURE n )NmATED TO SPECIlCATION 7EAR n #UPPING mAT SPOTS FEATHERING AND SHOULDER WEAR 4READ GROOVES n #ORRECT DEPTH OVER ENTIRE SURFACE 4YPE n 4HE TIRE IS THE PROPER APPLICATION &OREIGN DEBRIS n 3TONES MUD ETC s 7HEELS .OT DEFORMED OR BENT 7EIGHTS n 0ROPERLY INSTALLEDCORRECT SIZE 7HEEL BOLTS n 4ORQUED TO SPECIlCATION 4IRE BEAD n 5NIFORM s $RIVELINE .OT DAMAGED OR BENT 0ROPERLY MOUNTED AND SUPPORTED 0ROPERLY ALIGNED s %NGINE "ELTS AND ACCESSORIES FOR DAMAGE 0ROPERLY ALIGNED -OUNTS s %XHAUST .OT DAMAGED OR BENT 0ROPERLY ALIGNED
s #HECK THE CUSTOMER REPAIR ORDER BEFORE BEGINNING THE ROAD TEST )T IS IMPORTANT TO KNOW WHICH SPECIlC CONCERN THE CUSTOMER HAS WITH HISHER VEHICLE 4HIS PREVENTS CORRECTING THE WRONG CONCERN AND INCREASING THE COST OF THE REPAIR )F POSSIBLE ROAD TEST WITH THE CUSTOMER s $ONT BE MISLED BY THE REPORTED LOCATION OF THE NOISE OR VIBRATION 4HE CAUSE ACTUALLY MAY BE SOME DISTANCE AWAY s 2EMEMBER THAT THE VIBRATING BODY MAY GENERATE A SMALL VIBRATION ONLY 4HIS SMALL VIBRATION IN TURN MAY CAUSE A LARGER VIBRATION OR NOISE DUE TO THE VIBRATING BODYS CONTACT WITH OTHER COMPONENTS s #ONDUCT THE ROAD TEST ON A QUIET STREET WHERE SAFELY DUPLICATING THE NOISE OR VIBRATION IS POSSIBLE )T MUST BE POSSIBLE TO OPERATE THE VEHICLE AT THE SPEED IN WHICH THE CONDITION OCCURS )T IS BEST TO CONDUCT THE ROAD TEST ON A ROUTE THAT HAS BEEN PREVIOUSLY DRIVEN WITH KNOWN GOOD VEHICLES 4HIS ALLOWS FOR ANY ROAD IMPERFECTIONS IE ROAD SURFACES AND JOINTS FROM BEING THE SOURCE OF .6( CONCERNS s 4URN OFF THE RADIO AND THE BLOWER FOR THE HEATER AND AIR CONDITIONER UNLESS THE NOISE OR VIBRATION ONLY OCCURS WITH THE AIR CONDITIONING OR RADIO ON s $ETERMINE WHICH TEST EQUIPMENT IS NEEDED FOR THE ROAD TEST )F UTILIZING TEST EQUIPMENT DURING A ROAD TEST IT IS BEST PRACTICE TO HAVE AN ASSISTANT DRIVE WHILE THE EQUIPMENT IS BEING MONITORED AND THE RESULTS RECORDED s &OR COLD WEATHER CLIMATES BE AWARE THAT SNOW AND ICE CAN BE THE CAUSE OF .6( CONCERNS
0ROPERLY MOUNTED AND SUPPORTED
$IAGNOSIS 2OAD 4ESTING 4HE FOLLOWING ROAD TEST PROCEDURE ASSISTS IN CLASSIFYING AN .6( CONCERN INTO s %NGINE SPEED s 6EHICLE SPEED s 7HEEL SPEED %ACH OF THE FOLLOWING PROCEDURES HELPS TO ELIMINATE POSSIBLE COMPONENTS $EPENDING UPON THE CAUSE OF THE .6( CONCERN CERTAIN PROCEDURES MAY OR MAY NOT BE NECESSARY
3LOW !CCELERATION 4EST 4HE lRST VEHICLE CHECK TO DETERMINE A RELATED SYMPTOM OF AN .6( CONCERN IS THE SLOW ACCELERATION TEST 4HIS TEST IS USED TO IDENTIFY THE NOISE OR VIBRATION IF A ROAD TEST WITH THE CUSTOMER WAS NOT POSSIBLE 4HE STEPS OF THE SLOW ACCELERATION TEST ARE 3LOWLY ACCELERATE THE VEHICLE TO THE SPEED IN WHICH THE PROBLEM OCCURS .OTE THE VEHICLE SPEED AND THE ENGINE RPM
s 3LOW !CCELERATION 4EST
)F POSSIBLE DETERMINE THE FREQUENCY OF THE NOISE OR VIBRATION
s .EUTRAL #OAST $OWN 3PEED 4EST
#LASSIFY THE NOISE OR VIBRATION
s $OWNSHIFT 3PEED 4EST s 4ORQUE #ONVERTER 4EST s 3TEERING )NPUT 4EST s 3TEERING )NPUT 4EST s .EUTRAL 2UN 5P 4EST s %NGINE ,OADED 4EST s %NGINE !CCESSORY 4EST
$IAGNOSIS .EUTRAL #OAST $OWN 3PEED 4EST
$OWNSHIFT 3PEED 4EST
4HE NEXT VEHICLE CHECK WHEN PERFORMING THE ROAD TEST IS THE NEUTRAL COAST DOWN SPEED TEST 4HIS TEST DIVIDES THE POSSIBLE CAUSES OF THE NOISE OR VIBRATION INTO TWO CATEGORIES
4HIS VEHICLE CHECK HELPS TO CONlRM THE .6( CONCERN AS ENGINE SPEED RELATED 4HE STEPS OF THE DOWNSHIFT SPEED TEST ARE
s 6EHICLE SPEED RELATED s %NGINE SPEED RELATED s 7HEEL SPEED RELATED 4HE STEPS OF THE NEUTRAL COAST DOWN SPEED TEST ARE $RIVE THE VEHICLE AT A SPEED HIGHER THAN THE SPEED IN WHICH THE NOISE OR VIBRATION WAS OBVIOUS IN THE SLOW ACCELERATION TEST 0LACE THE VEHICLE IN .EUTRAL AND COAST DOWN THROUGH THE SPEED WHERE THE CONCERN OCCURS #LASSIFY THE .6( CONCERN AS EITHER VEHICLE SPEED RELATED OR ENGINE SPEED RELATED s )F THE NOISE OR VIBRATION EXISTS THEN THE CONCERN IS VEHICLE OR WHEEL SPEED RELATED 4HIS ELIMINATES THE ENGINE AND TORQUE CONVERTER AS POSSIBLE CAUSES s )F THE .6( CONCERN DID NOT OCCUR DURING THE NEUTRAL COAST DOWN SPEED TEST PERFORM A DOWNSHIFT SPEED TEST TO CONlRM THE CONCERN AS ENGINE SPEED RELATED
3TOP THE VEHICLE AND PLACE THE TRANSMISSION IN A LOWER GEAR $RIVE THE VEHICLE AT THE ENGINE RPM IN WHICH THE NOISE OR VIBRATION OCCURS s )F THE NOISE OR VIBRATION EXISTS THEN THE CONCERN IS ENGINE SPEED RELATED 4HIS ELIMINATES TIRES WHEELS BRAKES AND SUSPENSION COMPONENTS s )F NECESSARY REPEAT THE TEST USING OTHER GEARS AND .EUTRAL TO CONlRM THE RESULTS
4ORQUE #ONVERTER 4EST 4HIS VEHICLE CHECK DETERMINES HOW THE TORQUE CONVERTER CONTRIBUTES TO AN ENGINE SPEED RELATED CONDITION 4HE STEPS OF THE TORQUE CONVERTER TEST ARE $RIVE THE VEHICLE AT THE SPEED IN WHICH THE .6( CONCERN EXISTS /PERATE THE TORQUE CONVERTER BY TAKING IT IN AND OUT OF LOCK UP BY LIGHTLY DEPRESSING THE BRAKE PEDAL WHILE MAINTAINING VEHICLE SPEED #HECK FOR NOISE WHEN THE TORQUE CONVERTER IS NOT LOCKED UP
$IAGNOSIS 3TEERING )NPUT 4EST
3TEERING )NPUT 4EST
4HE NEXT ROAD TEST STEPS ARE THE TWO STEERING INPUT TESTS 4HESE TESTS DETERMINE IF THE WHEEL BEARINGS AND OTHER SUSPENSION COMPONENTS ARE CONTRIBUTING TO A SPEED RELATED CONDITION
0ERFORM THE 3TEERING )NPUT 4EST IF THE .6( CONDITION OCCURS WHEN TURNING ONLY 4HE STEPS OF 3TEERING )NPUT 4EST ARE
4HE STEPS OF THE 3TEERING )NPUT 4EST ARE $RIVE THE VEHICLE AT THE SPEED IN WHICH THE .6( CONCERN EXISTS -AKE WIDE SWEEPING TURNS IN BOTH DIRECTIONS s )F THE CONCERN GOES AWAY OR GETS WORSE WHEEL BEARINGS HUBS 5NIVERSAL *OINTS 5 JOINTS DRIVE AXLES CONSTANT VELOCITY JOINTS AND TIRE TREAD WEAR MAY BE THE COMPONENTS CAUSING THE CONCERN
$RIVE THE VEHICLE AT A SPEED HIGHER THAN THE SPEED AT WHICH THE NOISE OR VIBRATION OCCURS 0LACE THE VEHICLE IN .EUTRAL AND COAST DOWN THROUGH THE SPEED WHERE THE .6( CONCERN IS OBVIOUS WHILE MAKING WIDE SWEEPING TURNS IN BOTH DIRECTIONS s )F THE CONCERN EXISTS CHECK FOR WORN WHEEL BEARINGS SUSPENSION BUSHINGS CONSTANT VELOCITY JOINTS AND 5 JOINTS CONTAINED IN THE AXLES OF QUATTRO APPLICATIONS s )F THE VIBRATION DOES NOT OCCUR STOP THE VEHICLE AND ENGAGE THE TRANSMISSION TRANSAXLE !LTERNATELY ACCELERATE AND DECELERATE THROUGH THE SPEED AT WHICH THE .6( CONCERN APPEARS WHILE MAKING WIDE SWEEPING TURNS IN BOTH DIRECTIONS s )F THE CONCERN RETURNS THEN THE CAUSE IS DEPENDENT UPON ENGINE LOAD 4HE PROBABLE CAUSES ARE CONSTANT VELOCITY JOINTS OR 5 JOINTS CONTAINED IN THE AXLES OF QUATTRO APPLICATIONS AND LOOSE OR MISSING LUGNUTS s )F THE NOISE IS A hCLUNKING SOUND v ENGINE AND TRANSAXLE MOUNTS SUSPENSION BUSHINGS AND 5 JOINTS ARE PROBABLE CAUSES
$IAGNOSIS .EUTRAL 2UN 5P 4EST 0ERFORM THE .EUTRAL 2UN 5P 4EST IF THE .6( 4HE STEPS OF THE %NGINE ,OADED 4EST ARE CONCERN IS ENGINE SPEED RELATED 5SE THE TEST AS A FOLLOW UP TO THE DOWNSHIFT TEST OR WHEN THE "LOCK THE FRONT AND BACK WHEELS .6( CONCERN OCCURS AT IDLE 4HE STEPS ARE !PPLY THE PARKING AND SERVICE BRAKES )NCREASE THE ENGINE RPM WHILE IN 0ARK OR .EUTRAL
0UT THE TRANSMISSION IN $RIVE WHILE KEEPING THE BRAKES APPLIED
)F NECESSARY MAKE NOTE OF THE RPM AND FREQUENCY OF THE .6( CONCERN
)NCREASE THE ENGINE RPM TO THE RPM AT WHICH THE .6( CONCERN OCCURRED )F NECESSARY MAKE NOTE OF THE RPM AND FREQUENCY OF THE .6( CONCERN
%NGINE ,OADED 4EST 0ERFORM THE %NGINE ,OADED 4EST IF THE .6( CONCERN IS ENGINE SPEED RELATED 4HIS TEST MAY HELP REPRODUCE ENGINE SPEED RELATED CONCERNS NOT EVIDENT WITH THE NEUTRAL RUN UP OR NEUTRAL COAST DOWN SPEED TESTS 4HE ENGINE LOADED TEST ALSO IDENTIlES NOISE AND VIBRATION SENSITIVE TO ENGINE LOAD OR TORQUE 4HESE .6( CONCERNS OFTEN APPEAR DURING HEAVY ACCELERATION OR WHEN CLIMBING A HILL 7ARNING "LOCK THE FRONT AND BACK WHEELS OR INJURY TO PERSONNEL MAY RESULT $O NOT EXCEED lVE SECONDS WHEN PERFORMING THE ENGINE LOADED TEST OR DAMAGE TO THE TRANSMISSION TRANSAXLE MAY RESULT
2ETURN ENGINE TO IDLE 0UT THE TRANSMISSION IN 2EVERSE WHILE KEEPING THE BRAKES APPLIED )NCREASE THE ENGINE RPM TO THE RPM AT WHICH THE .6( CONCERN OCCURRED )F NECESSARY MAKE NOTE OF THE RPM AND FREQUENCY OF THE .6( CONCERN )MMEDIATELY AFTER ENGINE LOADED TEST RUN IN NEUTRAL FOR MINUTES AT A SLIGHTLY ELEVATED RPM TO COOL THE TRANSMISSION
)F THE CONCERN IS DElNITELY ENGINE SPEED RELATED PERFORM THE %NGINE !CCESSORY 4EST TO NARROW DOWN THE POSSIBLE SOURCE OF THE CONCERN
$IAGNOSIS %NGINE !CCESSORY 4EST 0ERFORM THE %NGINE !CCESSORY 4EST IF THE .6( CONCERN IS ENGINE SPEED RELATED 4HIS TEST HELPS LOCATE FAULTY BELTS AND ACCESSORIES THAT ARE CAUSING ENGINE SPEED RELATED .6( CONCERNS 4HE STEPS ARE "LOCK THE FRONT AND BACK WHEELS !PPLY THE PARKING AND SERVICE BRAKES 2EMOVE THE ACCESSORY DRIVE BELTS )NCREASE ENGINE RPM TO THE RPM AT WHICH THE .6( CONCERN OCCURRED s )F THE VIBRATION OCCURS THE BELTS AND ACCESSORIES ARE NOT THE SOURCE OF THE CONCERN s )F THE BELTS AND ACCESSORIES ARE THE SOURCE OF THE .6( CONCERN CONTINUE TO ADD OR REMOVE SPECIlC ACCESSORY BELTS TO LOCATE THE CONCERN
#AUTION 7ITH THE ACCESSORY BELT REMOVED s $O NOT DRIVE THE VEHICLE s $O NOT OPERATE THE ENGINE FOR EXTENDED PERIODS n 7ATER COOLED ALTERNATORS CAN FAIL n %NGINES CAN OVERHEAT
.OTES
%NGINE 6IBRATIONS %NGINE 3PEED 2ELATED 6IBRATIONS
4YPES OF %NGINE 6IBRATIONS
$URING THE INITIAL VEHICLE ROAD TEST USING THE ROAD TEST PROCEDURE THE VIBRATION CAUSING THE CONCERN WILL BE CLASSIlED INTO EITHER ENGINE SPEED RELATED OR VEHICLE SPEED RELATED 4HIS SECTION WILL BE USED WHEN THE VIBRATION IS FOUND TO BE ENGINE SPEED RELATED
-ANY .6( CONCERNS ARE RELATED TO THE ENGINE SYSTEMS 4HE OPERATION OF THE ENGINE CREATES A NATURAL VIBRATION )F ANY ONE COMPONENT IS SLIGHTLY OUT OF BALANCE THE NATURAL VIBRATION OF THE ENGINE IS COMPOUNDED %NGINE VIBRATION IS GENERALLY CAUSED BY ANY OF THE FOLLOWING
%NGINE SPEED RELATED VIBRATIONS ARE CAUSED BY A COMPONENT THAT IS DRIVEN BY THE ENGINE 4HESE COMPONENTS MAY BE PART OF THE ENGINE ASSEMBLY OR AN ENGINE ACCESSORY 5SING THE FREQUENCY OF THE VIBRATION AND MATHEMATICAL FORMULAS THE ENGINE SPEED RELATED VIBRATION CAN BE CLASSIlED INTO THESE CATEGORIES s %NGINE #OMPONENTS s %NGINE !CCESSORIES s %NGINE #YLINDERS &IRING &REQUENCY
s &IRST AND SECOND ORDER ENGINE IMBALANCE s %NGINE lRING FREQUENCY s %NGINE MOUNTS s %NGINE ACCESSORIES &IRST AND 3ECOND /RDER %NGINE )MBALANCE ! lRST ORDER ENGINE IMBALANCE IS CREATED WHEN ANY COMPONENT THAT ROTATES AT CRANKSHAFT SPEED IS OUT OF BALANCE OR HAS EXCESSIVE RUNOUT %XAMPLES ARE HARMONIC BALANCER mYWHEEL OR TORQUE CONVERTER IMBALANCE AND CYLINDER TO CYLINDER MASS DIFFERENCES )N RARE CASES THE CRANKSHAFT ITSELF MAY BE IMBALANCED "ALANCING THE COMPONENT OR CORRECTING THE RUNOUT MAY BRING THE VIBRATION TO AN ACCEPTABLE LEVEL &IRST ORDER ENGINE VIBRATIONS CAN BE OFFSET BY PROPER ARRANGEMENT OF CRANKSHAFT COUNTERWEIGHTS 3ECOND ORDER ENGINE IMBALANCE IS CAUSED BY THE UP AND DOWN MOTION OF THE PISTONS 4HIS REVERSAL OF MASS AND MOTION CREATES A NATURAL VIBRATION 3YMPTOMS OF ENGINE IMBALANCE INCLUDE s ! LOW SPEED SHAKE FELT BETWEEN AND RPM THAT HAS A FREQUENCY OF TO (Z s ! ROUGHNESS SOMETIMES FELT AND HEARD BETWEEN TO RPM AT A FREQUENCY OF TO (Z &IRST AND SECOND ORDER ENGINE IMBALANCES ARE USUALLY DETECTED DURING THE .EUTRAL 2UN 5P 4EST
%NGINE 6IBRATIONS (ALF /RDER %NGINE 6IBRATION ! HALF ORDER VIBRATION IS CREATED WHEN ANY COMPONENT THAT ROTATES AT HALF THE CRANKSHAFT SPEED IS OUT OF BALANCE OR HAS EXCESSIVE RUNOUT !N EXAMPLE OF THIS IS CAMSHAFT IMBALANCE "ALANCING THE COMPONENT OR CORRECTING THE RUNOUT MAY BRING THE VIBRATION TO AN ACCEPTABLE LEVEL
4ORQUE CONVERTER IMBALANCE IS ALSO A POSSIBILITY WHEN DEALING WITH AN ENGINE DEPENDENT .6( CONCERN !LTHOUGH RARE ON NEW VEHICLES THIS TYPE OF VIBRATION MAY APPEAR IF THE TORQUE CONVERTER HAD BEEN REPLACED OR INSTALLED INCORRECTLY DURING TRANSMISSION SERVICE !LSO INSPECT THE mEXPLATE FOR DAMAGE AS THIS COULD CAUSE NOISE OR VIBRATION
4ORQUE #ONVERTER !LTHOUGH NOT ACTUALLY AN ENGINE COMPONENT THE TORQUE CONVERTER ROTATES AT ENGINE SPEED AND ITS VIBRATION FREQUENCIES ARE OFTEN THE SAME AS THE ENGINE 4HE TORQUE CONVERTER IS A mUID COUPLING THAT USES TRANSMISSION mUID TO TRANSFER AND MULTIPLY ENGINE TORQUE TO THE INPUT SHAFT OF AN AUTOMATIC TRANSMISSION
4ORQUE #ONVERTER
4HE MOVEMENT OF THE mUID BETWEEN THE IMPELLER WHICH IS CONNECTED TO THE ENGINE AND THE TURBINE WHICH CONNECTS TO THE TRANSMISSION CAN SOMETIMES GENERATE A BEAT SOUND )F THIS IS THE CASE HOWEVER THE SOUND DISAPPEARS WHEN THE TORQUE CONVERTER CLUTCH ENGAGES MECHANICALLY LOCKING THE IMPELLER AND TURBINE TOGETHER !NOTHER .6( CONCERN THAT MAY BE CAUSED BY THE TORQUE CONVERTER IS VIBRATION DURING CLUTCH ENGAGEMENT )F THE CONVERTER CLUTCH DOES NOT APPLY SMOOTHLY IT MIGHT RESULT IN A JERKING OR SHAKING VIBRATION THAT CAN BE FELT THROUGHOUT THE VEHICLE 4HIS VIBRATION DISAPPEARS WHEN THE CLUTCH lNALLY ENGAGES COMPLETELY
#ONVERTER CLUTCH VIBRATIONS ALSO CAN OCCUR DURING DOWNSHIFTS AND COASTING IF THE CLUTCH FAILS TO RELEASE CORRECTLY )F A CONVERTER CLUTCH MALFUNCTION IS THE SUSPECTED CAUSE OF AN .6( CONCERN REFER TO THE APPROPRIATE SERVICE PUBLICATIONS FOR TRANSMISSION DIAGNOSTIC PROCEDURES
%NGINE 6IBRATIONS %NGINE -OUNTS 4HE lRST COMPONENTS THAT ISOLATE VIBRATION FROM THE ENGINE TO THE PASSENGER COMPARTMENT ARE ENGINE MOUNTS %NGINE AND TRANSMISSION MOUNTING CONSISTS OF A NUMBER OF RELATIVELY SMALL PARTS AND ARE SOMETIMES IGNORED WHEN TROUBLESHOOTING (OWEVER THESE PARTS ARE EXTREMELY IMPORTANT IN PREVENTING NOISE AND VIBRATION PRODUCED BY THE ENGINE 4ORQUE REACTION FORCE OF THE ENGINE ACTS DIRECTLY ON THE TRANSMISSION CAUSING ENGINE MOUNTS TO BE SUBJECTED TO A LARGE FORCE 4HEREFORE ENGINE MOUNTS MUST BE RIGID TO STABILIZE THE ENGINE /N THE OTHER HAND TO MINIMIZE INHERENT ENGINE VIBRATIONS AND NOISE DURING ALL ENGINE SPEEDS THE ENGINE MOUNTS ALSO MUST BE SOFT !NY FAULT IN THE ENGINE MOUNTING SYSTEM CAN LEAD DIRECTLY TO NOISE AND VIBRATION )NSPECT ENGINE MOUNTS FOR CRACKS OR DAMAGE TO THE INSULATOR AND THE BRACKET 'ROUNDED THE ENGINE MOUNTED BRACKET CONTACTING THE FRAME MOUNTED BRACKET OR STRAINED ENGINE MOUNTS MAY NOT ISOLATE ENGINE VIBRATIONS %LECTRO (YDRAULIC %NGINE -OUNT
%NGINE MOUNTS MUST BE INSTALLED CORRECTLY )F THE MOUNTS ARE INSTALLED INCORRECTLY OR INCORRECT PARTS ARE USED THEY CANNOT ABSORB ENGINE VIBRATION 4HE 23 ENGINE MOUNTS USE SEVERAL MOUNTING HOLES DEPENDING ON WHICH ENGINE OPTION IS INSTALLED IN THE VEHICLE 3ERVICE INFORMATION DETAILS THE PROCEDURE TO REMOVE AND INSTALL THE ENGINE MOUNTING BOLTS AND LOCATOR PINS 3EVERAL !UDI MODELS USE %LECTRO (YDRAULIC %NGINE -OUNT 3OLENOID 6ALVES 4HESE VALVES SOFTEN OR STIFFEN THE ENGINE MOUNTS DEPENDING UPON ENGINE OPERATING CHARACTERISTICS 4HE SYSTEM MAY BE THE SOURCE OF AN ENGINE VIBRATION AT IDLE IF NOT OPERATING PROPERLY #ONSULT !UDI SERVICE INFORMATION FOR DIAGNOSTIC PROCEDURES FOR THIS SYSTEM
%NGINE 6IBRATIONS !CCESSORY 6IBRATION %NGINE ACCESSORIES CAN BE A SOURCE OF ENGINE VIBRATION &OR EXAMPLE AIR CONDITIONING COMPRESSORS ARE SUSCEPTIBLE TO OVERCHARGING WHICH CAN RESULT IN AN .6( CONDITION !CCESSORY PULLEY MISALIGNMENT OR FAULTY COMPONENTS ALSO CAN CAUSE VIBRATIONS 7ITH THE ADVENT OF SERPENTINE BELTS IT IS NO LONGER POSSIBLE TO REMOVE BELTS ONE AT A TIME TO ISOLATE THE SOURCE COMPONENT "ECAUSE THE SERPENTINE BELT DRIVES ALL COMPONENTS ONE COMPONENT MAY AFFECT ANOTHER THROUGH RESONANCE )F REMOVING THE SERPENTINE BELT ELIMINATES THE VIBRATION REINSTALL THE BELT AND OPERATE EACH COMPONENT SEPARATELY "Y TURNING THE AIR CONDITIONING /. AND /&& OR BY TURNING THE STEERING WHEEL SOME COMPONENTS CAN BE ELIMINATED OR ISOLATED AS .6( SOURCES 7HEN DIAGNOSING ACCESSORY VIBRATION MAKE SURE THE SOURCE OF THE VIBRATION IS NOT CAUSED BY THE ENGINE OR ENGINE lRING FREQUENCIES %NGINE lRING FREQUENCIES CAN CAUSE COMPONENTS TO RESONATE AND VIBRATE 4HE VIBRATION AMPLITUDE MAY INCREASE WITH THE ACCESSORIES LOADED 4HE MOST EFFECTIVE REPAIR MAY BE ISOLATING THE DISTURBANCE BY INTERRUPTING ITS TRANSFER PATH RATHER THAN ATTEMPTING TO ELIMINATE THE SOURCE
%NGINE 6IBRATIONS %NGINE 6IBRATION &ORMULA &OR PURPOSES OF VIBRATION DIAGNOSIS THE ENGINE ALSO INCLUDES THE TORQUE CONVERTER AND EXHAUST SYSTEM 7HEN AN .6( PROBLEM IS TORQUE SENSITIVE THE VIBRATION MAY APPEAR OR DISAPPEAR AT DIFFERENT VEHICLE SPEEDS MPHKPH BUT IS PRESENT AT THE SAME ENGINE RPM &OR EXAMPLE IF A VEHICLE HAS SOME VIBRATION AT MPH KPH MPH KPH AND MPH KPH BUT IS WORSE AT A PARTICULAR SPEED THE .6( CONCERN IS PROBABLY TORQUE SENSITIVE SINCE THE CONDITION OCCURS AT THE SAME ENGINE RPM BUT AT A DIFFERENT LOAD 5SE THE ENGINE RPM AT WHICH THE .6( SYMPTOM OCCURS TO DETERMINE ENGINE FREQUENCY #ALCULATE ENGINE FREQUENCY AS FOLLOWS $IVIDE THE ENGINE RPM BY THE NUMBER OF SECONDS IN A MINUTE RP M ( Z E N G I N E F RE Q U E N C Y &OR EXAMPLE IF THE CORRESPONDING ENGINE RPM OF AN .6( PROBLEM ON A VEHICLE IS RPM THE RESULTING ENGINE FREQUENCY IS (Z
(Z 4O GET THE SECOND AND THIRD ORDER FREQUENCY MULTIPLY THE lRST ORDER FREQUENCY BY FOR SECOND ORDER FOR THIRD ORDER ETC &IRST ORDER X 3ECOND ORDER & I R S T O R D E R X 4 H I R D O R D E R %NGINE VIBRATIONS ALSO MAY HAVE HALF ORDER FREQUENCIES HALF ORDER FREQUENCIES ARE CALCULATED BY DIVIDING THE lRST ORDER BY &IRST ORDER (ALF ORDER
%NGINE 6IBRATIONS %NGINE !CCESSORY &ORMULA "ELT DRIVEN ENGINE ACCESSORIES PRODUCE VIBRATIONS AT DIFFERENT FREQUENCIES THAN THE ENGINE ITSELF 4HIS IS BECAUSE THE DRIVE RATIO CREATED BY THE DIFFERENT SIZE PULLEYS CAUSES THEM TO ROTATE AT DIFFERENT SPEEDS $ETERMINING ENGINE ACCESSORY FREQUENCY IS COMPARABLE TO CALCULATING DRIVELINE FREQUENCY #ALCULATE ENGINE ACCESSORY FREQUENCY BY PERFORMING THE FOLLOWING STEPS $ETERMINE THE SIZE RATIO BETWEEN THE ACCESSORY PULLEY AND THE CRANKSHAFT PULLEY BY DIVIDING THE CRANKSHAFT PULLEY DIAMETER BY THE ACCESSORY PULLEY DIAMETER # R A N K S H A FT P U L L E Y D I A M E T E R !CCESSORY PULLEY DIAMETER 0ULLEY RATIO &OR EXAMPLE IF THE DIAMETER OF THE CRANKSHAFT PULLEY IS MM INCHES AND THE ACCESSORY PULLEY DIAMETER IS MM INCHES DIVIDE BY 4HE ACCESSORY PULLEY ROTATES THREE TIMES FOR EVERY CRANKSHAFT ROTATION
-ULTIPLY THE ENGINE RPM IN WHICH THE .6( CONDITION OCCURS BY THE PULLEY RATIO % N G I N E RP M X 0 U L L E Y R A T I O ! C C E S S O R Y RP M &OR EXAMPLE IF THE ENGINE RPM IS RPM ENGINE SPEED MULTIPLY BY 4HE ACCESSORY IS ROTATING AT RPM X RP M $IVIDE THE ACCESSORY RPM BY THE NUMBER OF SECONDS IN A MINUTE TO OBTAIN THE ACCESSORY (Z ! C C E S S O R Y RP M ! C C E S S O R Y ( Z &OR EXAMPLE THE ENGINE ACCESSORY RPM IS DIVIDE BY 4HE ENGINE ACCESSORY FREQUENCY IS (Z (Z
! C C E S S O R Y ( Z
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%NGINE 6IBRATIONS 4YPES OF %NGINE .OISES 7HEN ENGINE COMPONENTS DEVIATE FROM THE PRECISE SPECIlCATIONS IN WHICH THEY WERE ENGINEERED THE ENGINE CREATES EXCESSIVE OR INTOLERABLE NOISES 2ECIPROCATING MOTION OF THE PISTONS AND THE ROTATING MOTION OF OTHER ENGINE COMPONENTS CREATE INHERENT NOISES #AUSES OF ENGINE NOISES INCLUDE
!BNORMAL #OMBUSTION !NY ABNORMALITIES IN THE COMBUSTION PROCESS CAN LEAD TO AUDIBLE ENGINE VIBRATIONS !BNORMAL COMBUSTION CAN INCLUDE ANY OF THE FOLLOWING s 3PARK KNOCK PINGING s "ACKlRING
s #OMBUSTION n .OISES ARE PRODUCED WHEN $ETONATION 0INGING THE AIRFUEL MIXTURE IS IGNITED 0INGING IS GENERALLY DISTINGUISHED BY A HIGH s &RICTION PITCHED STRIKING NOISE GENERATED WHEN THE THROTTLE IS FULLY OPEN OR DURING HARD ACCELERATION s -OVING PARTS AND THE IMPACT BETWEEN )F OPERATION IS CONTINUED IN THIS STATE THE RECIPROCATING PARTS PISTONS AND VALVES ARE ADVERSELY AFFECTED s 4OLERANCE hSLAPv n 0ISTONS MOVE UP AND RESULTING IN A DAMAGED ENGINE DOWN AND THE TOLERANCE BETWEEN PARTS IS REPEATEDLY PULLED IN ALTERNATING DIRECTIONS #AUSES OF ENGINE SPARK KNOCK PINGING INCLUDE THE FOLLOWING s )NADEQUATE FUEL s )NCORRECT TIMING s #ARBON DEPOSITS IN THE COMBUSTION CHAMBER
%NGINE 6IBRATIONS "ACKlRING
%XHAUST .OISE
/NE TYPE OF BACKlRE KNOWN AS POP BACK OCCURS 4HE EXHAUST SYSTEM CAN BE A SOURCE OF NOISE WHEN THE CYLINDER IS lRED BEFORE THE INTAKE %XHAUST NOISES INCLUDE VALVE CLOSES 7HEN THE INTAKE VALVE OPENS THE AIRFUEL MIXTURE IN THE INTAKE MANIFOLD IS IGNITED s %XHAUST GAS SOUNDS AND BURNS 4HIS SITUATION IS SOMETIMES VIOLENT s -UFmER AND PIPE ENOUGH TO CAUSE AN EXPLOSIVE REPORT WITHIN THE MANIFOLD 0OP BACK CAN BE CAUSED BY THE FOLLOWING %XHAUST GAS SOUNDS ARE FURTHER SUBDIVIDED INTO THREE CATEGORIES s %XCESSIVELY LEAN FUEL MIXTURE s )NCORRECT VALVE TIMING
s 0ULSATING s !IR COLUMN RESONANCE
)F THE MIXTURE IS TOO LEAN mAME SPEED s !IR STREAM SOUNDS BECOMES SLOWER TAKING LONGER TO COMPLETE THE COMBUSTION PROCESS )F TIMING HAS BEEN DISTURBED A POP BACK CAN OCCUR AND POSSIBLY THE %XHAUST GASES ARE DISCHARGED EACH TIME THE EXHAUST VALVES OPEN CREATING A PULSATING SOUND ENGINE WILL NOT START 4HE SOUND IS CYCLIC AND IS ASSOCIATED WITH !NOTHER TYPE OF BACKlRE IS AFTERlRE !FTERlRE IS ENGINE SPEED AND THE NUMBER OF CYLINDERS 4HE COMBUSTION IN THE EXHAUST SYSTEM PRODUCING A SOUND IS RELATIVELY LOW PITCHED CONSISTING MAINLY LOUD REPORT OR mAMES AT THE TAIL PIPE #ONDITIONS OF THIS BASIC FREQUENCY THAT CAN PRODUCE AFTERlRE ARE !IR COLUMN RESONANCE CONSISTS OF SOUNDS s $RIVING FOR PERIODS OF TIME WITH THE PRODUCED IN EXHAUST PIPES AND MUFmERS 0IPE ENGINE BRAKED LENGTH AND THE CROSS SECTIONAL AREA OF THE PIPE DETERMINE THE FREQUENCY !IR STREAM SOUNDS CAN s 4HE THROTTLE VALVE CLOSING RAPIDLY BE PRODUCED BY HIGH SPEED EXHAUST !N EXAMPLE OF THIS IS TURBULENCE CAUSED BY AIR GOING THROUGH !FTERlRE OCCURS WHEN UNBURNED FUEL IS RELEASED THE MUFmER OR JET NOISE WHEN EXHAUST IS DISCHARGED FROM THE TAILPIPE FROM THE COMBUSTION CHAMBER AND IS REHEATED BY COMPONENTS IN THE EXHAUST SYSTEM 7HEN -UFmER AND EXHAUST NOISES CAN BE CAUSED THE FUEL IS REHEATED PAST ITS SELF IGNITION POINT BY EXHAUST SYSTEM MISALIGNMENT INCORRECTLY AFTERlRE OCCURS )N SOME CASES AFTERlRE INSTALLED OR DAMAGED MOUNTING BRACKETS OR CAN CAUSE DAMAGE TO THE MUFmER CATALYTIC FAILED HANGERS 4HIS CAN CAUSE A VARIETY OF CONVERTER OR OTHER COMPONENTS OF THE EXHAUST ANNOYING NOISES THAT CAN BE LOCATED WITH A SYSTEM -AIN CAUSES OF AFTERlRE INCLUDE THOROUGH VISUAL INSPECTION s 2ICH FUEL MIXTURE s )NCORRECT IGNITION OR VALVE TIMING s &AULTY IGNITION COMPONENTS
!NY OF THESE SOUNDS IN THE EXHAUST SYSTEM CAN BE CARRIED OR TRANSMITTED THROUGHOUT MANY OF THE EXHAUST SYSTEM COMPONENTS AND INTO THE PASSENGER COMPARTMENT
%NGINE 6IBRATIONS #OMPELLING &ORCE OF %XHAUST
%XHAUST (ANGERS
4HE COMPELLING FORCE OF EXHAUST EXITING EACH CYLINDER CREATES A PULSATION ON THE EXHAUST MANIFOLD 4HE PULSATING PRESSURE AT THE EXHAUST MANIFOLD PRODUCES ACOUSTIC ENERGY WHICH IS TRANSMITTED TO THE EXHAUST PIPE 4HE PULSATING SOUND WAVES TRAVELING THROUGH THE EXHAUST PIPE ARE A SOURCE OF VIBRATION FOR THE EXHAUST SYSTEM %XHAUST VIBRATIONS CAN BECOME AMPLIlED BY RESONATING WITH ENGINE lRING FREQUENCIES AND VIBRATIONS CAUSED BY THE RECIPROCAL MOTION OF THE PISTONS 4HE COMBINATION OF THESE VIBRATIONS CAN PRODUCE UNWANTED .6( CONCERNS
4HE COMBINATION OF ENGINE EXHAUST AND ACOUSTIC VIBRATIONS WITHIN THE EXHAUST SYSTEM MUST BE DAMPENED )N ORDER TO DAMPEN THESE VIBRATIONS AND PREVENT THEM FROM ACTING ON THE BODY OF THE VEHICLE EXHAUST HANGERS MUST BE SPECIALLY DESIGNED %XHAUST HANGERS ARE DESIGNED TO SUSPEND THE EXHAUST PIPE FROM THE BODY AND TO PREVENT TRANSMISSION OF VIBRATION TO THE BODY %XHAUST HANGERS USUALLY CONSIST OF RIGID METAL TO SUPPORT THE SYSTEM SEPARATED BY RUBBER TO DAMPEN THE VIBRATION )DEALLY HANGERS SHOULD BE LOCATED FOR SUPPORT AT POINTS WHERE THEY BEAR THE WEIGHT OF THE EXHAUST UNIFORMLY 4HEY ARE ALSO LOCATED AT POINTS OF INHERENT MINIMUM VIBRATION 4HE LOCATION AND TENSION OF THE HANGER RUBBER AFFECTS THE PASSENGER COMPARTMENT NOISE LEVEL -AIN MUFmER HANGERS ARE DOUBLE VIBRATION PROOF 4HE BODY SIDE OF THE MOUNT IS INSTALLED WITH A RUBBER BRACKET AND THE MUFmER IS THEN SUPPORTED BY A HANGER
%XHAUST &LAP 3OME !UDI 44 ! AND ! MODELS HAVE AN EXHAUST mAP THAT IS CONTROLLED BY THE %NGINE #ONTROL -ODULE %#- 4HIS mAP WILL OPEN OR CLOSE DEPENDING ON EITHER ENGINE SPEED OR OTHER VEHICLE CONDITIONS 7HEN DIAGNOSING AN EXHAUST NOISE OR OTHER .6( CONCERN BE SURE THIS mAP IS OPERATING CORRECTLY AND IS NOT THE CAUSE OF ABNORMAL NOISES
%NGINE 6IBRATIONS %XHAUST 3YSTEM 3YMPTOMS AND #ORRECTIONS %XHAUST SYSTEM VIBRATIONS SYMPTOMS AND POSSIBLE CORRECTIONS ARE LISTED IN THE TABLE
%XHAUST 3YSTEM .6( #ONCERNS #/.$)4)/.
39-04/-
#/22%#4)/.
5NPLEASANT DRONING
'ENERATED WHEN EXHAUST SYSTEM VIBRATION IS TRANSMITTED THROUGH EXHAUST PIPE HANGERS AND ENGINE MOUNTS TO THE BODY #AUSES BODY PANELS AND FRAMES TO VIBRATE
)NSPECT EXHAUST PIPE HANGERS AND ENGINE MOUNTS FOR DAMAGE 4IGHTEN OR REPLACE AS NECESSARY
/UTSIDE PASSENGER COMPARTMENT RADIATING NOISE
.OISE PRODUCED BY VIBRATION OF EXHAUST SYSTEM PIPES MUFmER SHELL END PLATE SEPARATOR EXHAUST PIPE OR SHIELD PLATE %NGINE RACING CAN REPRODUCE THIS NOISE
)DENTIFY EXHAUST COMPONENTS RESPONSIBLE FOR THE NOISE AND CHECK FOR LOOSENESS DAMAGE OR INTERFERENCE !DJUST OR REPLACE AS NECESSARY
)DLING VIBRATION
(EAVY DEFORMATION OF EXHAUST PIPES OR mEXIBLE TUBES COLLAPSED mEXIBLE TUBES CAN CHANGE VIBRATION CHARACTERISTICS OF THE EXHAUST SYSTEM INDUCING IDLING VIBRATION
2EPLACE DAMAGED OR DEFORMED EXHAUST COMPONENT
%NGINE 6IBRATIONS %NGINE &IRING &REQUENCY !LL ENGINES HAVE INHERENT lRST ORDER VIBRATIONS %NGINES ALSO HAVE VIBRATIONS CREATED BY lRING FREQUENCY &IRING FREQUENCY REFERS TO THE FORCE CREATED BY THE ENGINE EACH TIME A CYLINDER lRES 4HE FORCE OF THE COMBUSTION CREATES ONE PULSE AND WITH THE CYLINDERS lRING IN ORDER A NATURAL VIBRATION IS CREATED 4HE HIGHER THE LOAD AN ENGINE IS UNDER THE MORE PROMINENT THE lRING FREQUENCY BECOMES 6IBRATIONS ALSO INCREASE WHEN THE ENGINE HAS A PROBLEM THAT INTERFERES WITH THE NORMAL COMBUSTION CYCLE 3YMPTOMS OF lRING FREQUENCY .6( CONCERNS INCLUDE s %NGINE RPM SENSITIVITY s 4ORQUE SENSITIVITY s ,OW FREQUENCY NOISE s 3HAKE OR BUZZ s ,OADED ENGINE )F AN .6( CONCERN IS lRING FREQUENCY SENSITIVE IT MAY BE CAUSING RESONANCE OF ANOTHER COMPONENT WHEN A SPECIlC RPM IS REACHED &IRING FREQUENCY CONCERNS USUALLY HAVE A NARROW RPM RANGE 4O PREVENT THE VIBRATIONS CREATED BY lRING PULSES FROM BECOMING AN .6( CONCERN THE VIBRATION MUST BE ISOLATED -OTOR MOUNTS ARE DESIGNED TO MINIMIZE THE AMOUNT OF VIBRATIONS THAT REACH THE PASSENGER COMPARTMENT
%NGINE 6IBRATIONS %NGINE &IRING &REQUENCY &ORMULA %NGINE lRING FREQUENCY IS A TERM USED TO DESCRIBE THE PULSES AN ENGINE CREATES FROM THE lRING OF THE CYLINDERS %NGINE lRING FREQUENCY DEPENDS UPON HOW MANY CYLINDERS AN ENGINE HAS 4HE NUMBER OF TIMES AN ENGINE lRES A CYLINDER WITH EACH CRANKSHAFT REVOLUTION IS EQUAL TO ONE HALF THE NUMBER OF CYLINDERS ! FOUR CYLINDER ENGINE lRES TWO CYLINDERS WITH EACH CRANKSHAFT REVOLUTION 4WO REVOLUTIONS OF THE CRANKSHAFT lRES ALL FOUR CYLINDERS ! SIX CYLINDER ENGINE lRES THREE CYLINDERS WITH EACH CRANKSHAFT REVOLUTION !N EIGHT CYLINDER ENGINE lRES FOUR CYLINDERS FOR EACH CRANKSHAFT REVOLUTION #ALCULATE THE ENGINE lRING FREQUENCY BY PERFORMING THE FOLLOWING STEPS $IVIDE THE ENGINE RPM AT WHICH THE VIBRATION OCCURS BY RP M % N G I N E ( Z &OR EXAMPLE RP M ( Z -ULTIPLY ENGINE FREQUENCY BY HALF OF THE NUMBER OF CYLINDERS IN THE ENGINE &OR A FOUR STROKE ENGINE
%NGINE (Z X (ALF THE NUMBER OF C Y L I N D E R S % N G I N E F I RI N G ( Z &OR EXAMPLE X SIX CYLINDER ENGINE % N G I N E & I RI N G ( Z
6EHICLE 3PEED 6IBRATIONS 6EHICLE 3PEED 2ELATED 6IBRATIONS
4IRES AND 7HEELS
$URING THE INITIAL VEHICLE ROAD TEST USING THE ROAD TEST PROCEDURES THE VIBRATION CAUSING THE CONCERN WILL BE CLASSIlED INTO EITHER ENGINE SPEED RELATED OR VEHICLE SPEED RELATED 4HIS SECTION WILL BE USED WHEN THE VIBRATION IS FOUND TO BE VEHICLE SPEED RELATED
.OISE AND VIBRATION THAT OCCUR DURING DRIVING HAVE VARIOUS SOURCES 4HE MAJOR SOURCES ARE THE FOLLOWING
6EHICLE SPEED RELATED VIBRATIONS ARE CAUSED BY A COMPONENT THAT IS ROTATING AT VEHICLE SPEED 4HESE COMPONENTS MAY BE PART OF THE TIRE AND WHEEL ASSEMBLIES OR A DRIVE TRAIN COMPONENT TRANSMITTING POWER TO THE WHEELS 4HERE ARE DRIVE TRAIN COMPONENTS THAT ROTATE AT TIRE AND WHEEL FREQUENCIES IE AXLE SHAFTS OR BRAKE COMPONENTS 4HE VIBRATION CAN BE DIAGNOSED TO ANOTHER COMPONENT ROTATING AT TIRE FREQUENCIES BY SUBSTITUTING TIRES AND WHEELS OF THE SAME TYPE FROM A KNOWN GOOD VEHICLE 4HESE COMPONENTS WILL NEED TO BE DIAGNOSED AFTER A TIRE FREQUENCY VIBRATION CANNOT BE CORRECTED BY SERVICING THE TIRE AND WHEEL ASSEMBLIES 5SING THE FREQUENCY OF THE VIBRATION AND MATHEMATICAL FORMULAS THE VEHICLE SPEED RELATED VIBRATION CAN BE CLASSIlED INTO THESE CATEGORIES
s 2OUGH OR IRREGULAR ROAD SURFACES s #ONDITION OF THE TIRES AND WHEELS )MPACT FORCE CAUSED BY ROUGH AND IRREGULAR ROAD SURFACES IS lRST TRANSMITTED TO THE TIRES CAUSING THEM TO VIBRATE 4HIS CHARACTERISTIC REPRESENTS THE CLOSE RELATIONSHIP THAT EXISTS BETWEEN THE TIRE AND ROAD SURFACE 4IRES JUST LIKE THE SUSPENSION BODY AND OTHER COMPONENTS ARE DESIGNED TO MINIMIZE NOISE AND VIBRATION (OWEVER THEY WEAR FASTER THAN OTHER COMPONENTS 4HIS IS A CONTRIBUTING FACTOR TO TIRE AND WHEEL NOISE AND VIBRATION 4IRES AND WHEELS CAN CAUSE VEHICLE VIBRATIONS FOR ONE OR MORE OF THE FOLLOWING REASONS s )MBALANCE s %XCESSIVE RADIAL FORCE VARIATION s %XCESSIVE RADIAL RUNOUT
s 4IRE AND 7HEEL !SSEMBLY s $RIVE 4RAIN #OMPONENT
s %XCESSIVE LATERAL RUNOUT s )MPROPERLY MOUNTED WHEEL ON THE VEHICLES HUB /NE OR MORE OF THE FOLLOWING TIRE PROPERTIES CAN CAUSE TIRE NOISE s .ATURAL FREQUENCY AND VIBRATION TRANSFER CHARACTERISTICS s 4READ PATTERNS
6EHICLE 3PEED 6IBRATIONS )MBALANCE
3TATIC "ALANCING
7HEN THE TIRE AND WHEEL ASSEMBLY ARE ROTATING AT NORMAL HIGHWAY SPEEDS IMBALANCE CONDITIONS ARE MOST LIKELY TO BE NOTICED BY THE DRIVER AND THE OCCUPANTS OF THE PASSENGER COMPARTMENT 4HE lRST STEP IN CORRECTING A TIRE AND WHEEL VIBRATION IS TO BALANCE THE TIRE AND WHEEL ASSEMBLY 4HERE ARE TWO METHODS FOR BALANCING TIRE AND WHEEL ASSEMBLIES 4HEY ARE
!S THE WORD STATIC IMPLIES THE TIRE WILL BE BALANCED WHEN AT REST &OR EXAMPLE IF AN UNMOVING ASSEMBLY WAS CENTERED ON A CONE AND WAS BALANCED IT WOULD BE STATICALLY BALANCED ! hBUBBLE BALANCERv IS DESIGNED TO STATICALLY BALANCE A TIRE AND WHEEL ASSEMBLY
s 3TATIC "ALANCING s $YNAMIC "ALANCING
3TATIC IMBALANCE IS WHERE THERE IS ONE AMOUNT OF WEIGHT LOCATED IN THE CENTER OF THE TIRE AND WHEEL ASSEMBLY CAUSING AN IMBALANCE !S THE WEIGHT ROTATES CENTRIFUGAL FORCES ARE CREATED CAUSING THE WHEEL TO LIFT AS THE WEIGHT REACHES TOP DEAD CENTER 4HIS LIFTING MOTION CAUSES THE TIRE AND WHEEL ASSEMBLY TO MOVE hUP AND DOWNv CREATING A BOUNCE TO BE FELT 4HE STATIC IMBALANCE CONDITION IS EVIDENT BY A hJIGGLEv OR UP DOWN MOVEMENT OF THE STEERING WHEEL 4HESE VIBRATIONS MAY ALSO BE APPARENT IN THE BODY WITH OR WITHOUT STEERING WHEEL SHAKE ! STATICALLY IMBALANCED TIRE DRIVEN FOR AN EXTENDED PERIOD MAY CAUSE hCUPPINGh IN THE TIRES TREAD CREATE VIBRATION AND ADVERSELY AFFECT HANDLING 3TATIC BALANCING ALONE IS A SELDOM RECOMMENDED PROCEDURE THAT BALANCES THE ASSEMBLY USING ONLY A SINGLE WEIGHT PLANE &OR EXAMPLE A SINGLE WEIGHT IS COMMONLY PLACED ON THE INNER CLIP WEIGHT POSITION FOR COSMETIC PURPOSES 4HIS IS NOT A RECOMMENDED PRACTICE AND USUALLY RESULTS IN AN ASSEMBLY THAT IS NOT DYNAMICALLY BALANCED 4HE ASSEMBLY MAY THEN EXPERIENCE SIDE TO SIDE IMBALANCE WHILE IN MOTION CAUSING A SHIMMY CONDITION AND OBJECTIONABLE VIBRATION
6EHICLE 3PEED 6IBRATIONS $YNAMIC "ALANCING $YNAMIC IMBALANCE IS DElNED WHERE ONE OR MORE LOCATIONS OF THE TIRE AND WHEEL ASSEMBLY ARE HEAVIER CAUSING AN IMBALANCE FORCE OR AN IMBALANCE WOBBLE 4HE EXAMPLE SHOWN IS A TIRE AND WHEEL ASSEMBLY WITH TWO HEAVY SPOTS OF EQUAL WEIGHT WHICH ARE LOCATED DEGREES ACROSS FROM EACH OTHER ON OPPOSITE SIDES !S THIS ASSEMBLY ROTATES CENTRIFUGAL FORCES CAUSE A LARGE IMBALANCE WOBBLE TO BE CREATED BUT THE IMBALANCE FORCE AS WELL AS THE STATIC IMBALANCE WILL BE ZERO ! WHEEL WITH THIS CONDITION WILL CAUSE A WOBBLE OR SHIMMY TO BE FELT IN THE STEERING WHEEL %XCESSIVE DYNAMIC IMBALANCE OF THIS TYPE CREATES A SHIMMY THAT TRANSFERS THROUGH THE SUSPENSION COMPONENTS TO THE OCCUPANTS OF THE VEHICLE ESPECIALLY AT HIGHER SPEEDS $YNAMIC BALANCERS SPIN THE WHEEL IN ORDER TO MEASURE BOTH THE UP AND DOWN IMBALANCE FORCE AND THE WOBBLE OR SHIMMY RELATED IMBALANCE SIDE TO SIDE $YNAMIC BALANCERS DIRECT THE OPERATOR TO PLACE CORRECTION WEIGHTS ON THE INSIDE AND OUTSIDE CORRECTION LOCATIONS OF THE RIM SO THAT BOTH IMBALANCE FORCE AND IMBALANCE WOBBLE WILL BE ELIMINATED
6EHICLE 3PEED 6IBRATIONS -ECHANICAL 5NLOADED 2UNOUT 2UNOUT OF A TIRE AND WHEEL ASSEMBLY DIRECTLY AFFECTS THE AMOUNT OF IMBALANCE AND RADIAL FORCE VARIATION AND SHOULD BE CORRECTED lRST 4HE SMALLER THE AMOUNT OF RUNOUT THE LESS IMBALANCE AND FORCE VARIATION 2ADIAL AND LATERAL RUNOUT CAN BE CORRECTED AT THE SAME TIME 4HERE ARE TWO METHODS TO MEASURE RUNOUT OF THE TIRE AND WHEEL ASSEMBLY s /N VEHICLE s /FF VEHICLE 0RIOR TO PERFORMING A RUNOUT MEASUREMENT ENSURE THAT THE BEADS ARE SEATED EQUALLY AROUND THE CIRCUMFERENCE OF THE TIRE /N VEHICLE MEASUREMENTS REQUIRE THE WHEEL TO BE MOUNTED ONTO THE HUB AND THAT THE WHEEL BEARING IS IN GOOD CONDITION /NCE THE ON VEHICLE RUNOUT HAS BEEN CHECKED THEN ON OFF VEHICLE CHECK SHOULD BE TAKEN )F THERE IS A LARGE DIFFERENCE BETWEEN RUNOUT MEASUREMENTS ON THE VEHICLE AND OFF THE VEHICLE THEN RUNOUT IS DUE TO ONE OF THE FOLLOWING s 3TUD CIRCLE RUNOUT s (UB mANGE RUNOUT s 3OME OTHER MOUNTING CONDITION BETWEEN THE WHEEL AND THE VEHICLE 7HEN DIAGNOSING A TIRE AND WHEEL CONCERN ON A VEHICLE CONSULT THE SERVICE INFORMATION FOR CORRECT SPECIlCATIONS
6EHICLE 3PEED 6IBRATIONS -ECHANICAL 5NLOADED 2ADIAL 2UNOUT
-ECHANICAL 5NLOADED ,ATERAL 2UNOUT
2ADIAL RUNOUT OF THE TIRE AND WHEEL ASSEMBLY SHOULD BE STARTED AT THE TIRE WHILE MOUNTED TO THE VEHICLE )F THE TIRE RADIAL RUNOUT MEASUREMENTS ARE WITHIN SPECIlCATIONS NO FURTHER RADIAL MEASUREMENTS OF THE ASSEMBLY NEED TO BE MEASURED
,ATERAL RUNOUT OF THE TIRE AND WHEEL ASSEMBLY SHOULD BE STARTED AT THE TIRE WHILE MOUNTED TO THE VEHICLE )F THE TIRE LATERAL RUNOUT MEASUREMENTS ARE WITHIN SPECIlCATIONS NO FURTHER LATERAL MEASUREMENTS OF THE ASSEMBLY ARE NEEDED
)F THE RADIAL RUNOUT MEASUREMENTS EXCEED SPECIlCATIONS WHILE MOUNTED ON THE VEHICLE PERFORM THE MEASUREMENTS OFF VEHICLE 4HE TIRE AND WHEEL ASSEMBLY RADIAL RUNOUT CAN BE MEASURED OFF VEHICLE WHEN MOUNTED ON A BALANCING MACHINE
)F THE LATERAL RUNOUT MEASUREMENTS EXCEED SPECIlCATIONS WHILE MOUNTED ON THE VEHICLE PERFORM MEASUREMENTS OFF VEHICLE 4HE TIRE AND WHEEL ASSEMBLY LATERAL RUNOUT CAN BE MEASURED OFF VEHICLE WHEN MOUNTED ON A BALANCING MACHINE
)F THE OFF VEHICLE RUNOUT EXCEEDS SPECIlCATIONS RADIAL RUNOUT OF THE STUD CIRCLE AND HUB mANGE NEEDS TO BE MEASURED 4HE WHEEL TO HUB MOUNTING SHOULD BE CHECKED TO ENSURE THERE ARE NO FAULTS CAUSING THE RUNOUT
)F THE OFF VEHICLE RUNOUT EXCEEDS SPECIlCATIONS LATERAL RUNOUT OF THE STUD CIRCLE AND HUB mANGE NEEDS TO BE MEASURED 4HE WHEEL TO HUB MOUNTING SHOULD BE CHECKED TO ENSURE THERE ARE NO FAULTS CAUSING THE RUNOUT
)F THE OFF VEHICLE MEASUREMENT EXCEEDS SPECIlCATIONS THE RADIAL RUNOUT OF THE WHEEL ASSEMBLY SHOULD BE TAKEN )F THE WHEEL ASSEMBLY EXCEEDS SPECIlCATIONS IT WILL NEED TO BE REPLACED )F THE WHEEL ASSEMBLY MEETS SPECIlCATIONS THE TIRE IS AT FAULT AND WILL NEED TO BE REPLACED
)F THE OFF VEHICLE MEASUREMENT EXCEEDS SPECIlCATIONS THE LATERAL RUNOUT OF THE WHEEL ASSEMBLY SHOULD BE TAKEN )F THE WHEEL ASSEMBLY EXCEEDS SPECIlCATIONS IT WILL NEED TO BE REPLACED )F THE WHEEL ASSEMBLY MEETS SPECIlCATIONS THE TIRE IS AT FAULT AND WILL NEED TO BE REPLACED
6EHICLE 3PEED 6IBRATIONS 2ADIAL &ORCE 6ARIATION 2&6 4HE 2&6 IS AN INDUSTRIAL MEASUREMENT TERM DESCRIBING THE TIRE UNIFORMITY UNDER LOAD MEASURING THE VARIATION UP AND DOWN OF THE LOAD ACTING ON THE VEHICLE SPINDLE !LL TIRES HAVE SOME NON UNIFORMITY IN THE SIDEWALL ANDOR FOOTPRINT DUE TO VARIABLES IN THE MANUFACTURING PROCESS 4IRE UNIFORMITY MEASUREMENT VALUES CAN BE AFFECTED BY RIM WIDTH RIM CONDITION AND MANY DIVERSE TIRE MOUNTING VARIABLES 5NLIKE BALANCING THERE IS OFTEN A SMALL AMOUNT OF 2&6 REMAINING IN THE TIRE AND WHEEL ASSEMBLY AFTER ASSEMBLY AND THIS IS GENERALLY ACCEPTABLE 4O UNDERSTAND THE EFFECTS OF RADIAL FORCE VARIATION ON VIBRATION A MODEL OF A TIRE CAN BE USED 4HE SIDEWALL AND FOOTPRINT CAN BE UNDERSTOOD AS A COLLECTION OF SPRINGS BETWEEN THE RIM AND THE TIRE CONTACT PATCH )F THE hSPRINGSv ARE NOT OF UNIFORM STIFFNESS A VARIED FORCE IS EXERTED ON THE AXLE AND CAUSES IT TO MOVE UP AND DOWN AS THE TIRE ROTATES AND mEXES 4HIS MOVEMENT CREATES A VIBRATION IN THE VEHICLE UNRELATED TO BALANCE ! TIRE WITH NOTICEABLE 2&6 WILL PRODUCE A VIBRATION EVEN THOUGH IT IS PERFECTLY BALANCED AND IS WITHIN THE RADIAL AND LATERAL RUNOUT LIMITS -ANUFACTURERS ATTEMPT TO MINIMIZE THE 2&6 DURING TIRE AND WHEEL ASSEMBLY
4HE 2&6 CAN BE MEASURED BY A LOAD ROLLER PRESSING AGAINST A ROTATING TIRE AND WHEEL ASSEMBLY TO EVALUATE THE MAGNITUDE OF EXISTING ASSEMBLY HARMONICS 4HE (UNTER '30 3ERIES 6IBRATION #ONTROL 3YSTEM IS ONE METHOD OF DETERMINING AND POSSIBLY CORRECTING FOR 2&6 0AINT MARKS OR TAPE STRIPS ON THE TIRE AND WHEEL OR VALVE STEM LOCATION IN THE WHEEL VARY IN PURPOSE -ANUFACTURERS USE THESE MARKINGS FOR HEAVY SPOT 2&6 RUNOUT INVENTORY CONTROL AND SIMILAR PURPOSES 7ITHOUT SPECIlC MANUFACTURER INFORMATION THEY ARE OF LITTLE USE TO THE TECHNICIAN
6EHICLE 3PEED 6IBRATIONS .ATURAL &REQUENCY AND 6IBRATION 4RANSFER #HARACTERISTICS
4READ 0ATTERNS
4IRE NOISE ASSOCIATED WITH TREAD PATTERNS HAS 7HEN A TIRE IS SUBJECTED TO A COMPELLING FORCE TWO CAUSES AT ONE POINT IT ONLY VIBRATES THERE AS LONG AS THE FREQUENCY OF THE COMPELLING FORCE IS LOW s 2EPEATED DEFORMATION OF THE TREAD BELOW (Z 7HEN THE FREQUENCY IS HIGH THE PATTERN GROOVES THAT OCCURS AS THE TIRE WHOLE TIRE STARTS TO VIBRATE 3IMILAR VIBRATIONS ARE ROLLS ON THE ROAD COMBINED WITH THE CAUSED WHEN TIRES ARE EXCITED BY ROAD SURFACE RESULTANT mOW OF AIR IN THE GROOVES IRREGULARITIES 4HESE VIBRATIONS HAVE A LARGE EFFECT s #ONTINUOUS STRIKING OF THE TREAD PATTERN ON UNWANTED HARSHNESS AND ROAD NOISE AGAINST THE ROAD SURFACE 4HE RELATIONSHIP BETWEEN VIBRATION TRANSMISSIBILITY AND EXCITATION FREQUENCY IS CALLED THE hVIBRATION TRANSFER CHARACTERISTICv ! SMOOTH TREAD HAVING NO PATTERN ON THE SURFACE 4HIS IS A MEASURE OF A TIRES OVERALL VIBRATION IS THE MOST SILENT 4HE NOISE LEVELS OF THE TIRE CHARACTERISTIC 2ADIAL AND BIAS TIRES HAVE A TREAD INCREASES IN THE ORDER OF NATURAL FREQUENCY BETWEEN AND (Z RESPECTIVELY 4HE POOR HARSHNESS CHARACTERISTICS 3TRAIGHT RIB WITH GROOVES RUNNING AROUND THE CIRCUMFERENCE OF A RADIAL TIRE ARE DUE TO HIGH TRANSMISSION OF VIBRATIONS AT LOW NATURAL FREQUENCIES OF ABOUT 'ENERAL PURPOSE RIB WITH THE ZIGZAG GROOVES (Z /N THE OTHER HAND THE POOR ROAD NOISE CHARACTERISTICS OF A BIAS TIRE ARE DUE TO HIGH VIBRATION TRANSMISSIBILITY AT NATURAL FREQUENCIES 4IRE NOISE ASSOCIATED WITH TREAD PATTERNS WILL NEAR (Z CHANGE PITCHES WHEN DRIVEN ON DIFFERENT ROAD 4IRE AND WHEEL .6( CONCERNS ARE LOW FREQUENCY SURFACES $IAGNOSING TIRE NOISE IS ACCOMPLISHED BY DRIVING THE VEHICLE ON DIFFERENT TYPES OF ROAD USUALLY AROUND TO (Z +NOWING THE SURFACES IE ASPHALT AND CONCRETE 4HE TIRE NATURAL FREQUENCY AND VIBRATION TRANSFER NOISE WILL STILL BE PRESENT HOWEVER IT WILL SOUND CHARACTERISTICS OF DIFFERENT TIRES CAN HELP DIFFERENT ON THE DIFFERENT ROAD SURFACES 3IMILAR DETERMINE IF AN .6( CONCERN IS DUE TO THE TIRE VEHICLES WITH THE SAME TYPE TIRES WILL ALSO TYPE OR IF THE TIRE IS IN NEED OF SERVICE BECAUSE EXHIBIT THE SAME NOISE CHARACTERISTICS OF A RUNOUT OR IMBALANCE CONDITION
6EHICLE 3PEED 6IBRATIONS 4IRE 6IBRATION &ORMULAS 4O DETERMINE IF A VEHICLE SPEED RELATED VIBRATION IS BEING CAUSED BY A TIRE AND WHEEL ASSEMBLY USE THE TIRE VIBRATION FORMULAS 4IRE AND WHEEL CALCULATIONS ARE PERFORMED IN MPH KPH INCREMENTS "EGIN BY CALCULATING THE NUMBER OF TIRE AND WHEEL ROTATIONS IN MPH KPH INCREMENTS 4HE NEXT STEP IS TO CALCULATE THE 203 PER EVERY MPH KPH 4HEN CALCULATE THE VEHICLE SPEED WHERE THE VIBRATION OCCURS IN MPH KPH INCREMENTS AND CALCULATE THE TIRE AND WHEEL ASSEMBLY (Z RATE AT THE VIBRATION SPEED 4IRE 2EVOLUTIONS PER MPH KPH &ORMULA 5SE THE FOLLOWING FORMULA TO DETERMINE THE 203 PER MPH KPH
! N S W E R A B O V E 7 H E E L D I A M E T E R v M M 4 I RE D I A M E T E R $ETERMINE 203 IN MPH KPH INCREMENTS USING THE FOLLOWING FORMULA
$IVIDE BY THE TIRE DIAMETER
-ULTIPLY THE ABOVE ANSWER BY
$IVIDE THE ABOVE ANSWER BY
6ERIFY THE TIRE SIZE ON THE VEHICLE $ETERMINE TIRE DIAMETER BY USING THE FOLLOWING FORMULA
-ULTIPLY THE TIRE ASPECT RATIO BY THE TIRE WIDTH
$IVIDE THE ABOVE ANSWER BY
-ULTIPLY THE ABOVE ANSWER BY
!DD THE ABOVE ANSWER TO THE WHEEL DIAMETER
%XAMPLE 02 ! S P E C T R A T I O X 4 I RE W I D T H X
%XAMPLE 02 4 I RE D I A M E T E R !NSWER ABOVE X X !NSWER ABOVE 2 0 3 A T M P H K P H 4HIS FORMULA HAS DETERMINED THAT A 02 TIRE REVOLVES TIMES PER SECOND FOR EVERY MPH KPH INCREMENT 5SING THE 203 PER MPH KPH THE (Z RATE OF THE TIRE AND WHEEL ASSEMBLY AT A GIVEN VEHICLE SPEED CAN NOW BE DETERMINED 5SE THE 4IRE AND 7HEEL (: &ORMULA TO CALCULATE THE (Z RATE AT A GIVEN VEHICLE SPEED
!NSWER ABOVE !NSWER ABOVE X X
6EHICLE 3PEED 6IBRATIONS 4IRE AND WHEEL (Z &ORMULA 5SE THE TIRE AND WHEEL (Z FORMULA TO CALCULATE A -ULTIPLY THE VEHICLE MPH KPH INCREMENT TIRE AND WHEEL (Z RATE AT A GIVEN VEHICLE SPEED BY THE TIRE AND WHEEL 203 PER MPH KPH 2EMEMBER ALL TIRE AND WHEEL CALCULATIONS ARE DETERMINED IN MPH KPH INCREMENTS
"EGIN TO CALCULATE TIRE AND WHEEL FREQUENCY IN MPH KPH INCREMENTS BY PERFORMING THE FOLLOWING STEPS $IVIDE VEHICLE SPEED MPH BY KPH BY
4HIS STEP IS NECESSARY DUE TO ALL CALCULATIONS BEING DONE IN MPH KPH INCREMENTS 6E H I C L E S P E E D M P H I N C RE M E N T
&OR EXAMPLE IF THE CORRESPONDING SPEED OF AN .6( PROBLEM ON A VEHICLE IS MPH KPH THE RESULTING MPH KPH INCREMENT IS NINE M P H I N C RE M E N T S
5SE THE 4IRE 2EVOLUTIONS AT -0( +0( &ORMULA PREVIOUS PAGE TO DETERMINE THE TIRE AND WHEEL 203 PER MPH KPH
%XAMPLE FROM PREVIOUS PAGE )F THE TIRE SIZE ON THE VEHICLE IS 02 THEN THE 203 PER MPH KPH IS
4HIS DETERMINES HOW MANY TIMES THE TIRE AND WHEEL ASSEMBLY REVOLVES PER SECOND AT THE VEHICLE SPEED WHERE THE VIBRATION OCCURS
M P H I N C RE M E N T X 4 I RE 2 0 3 M P H TI RE A N D W H E E L 20 3 A T V I B RA T I O N SP EED
%XAMPLE 02 AT MPH X 2 0 3 A T M P H
4HE TIRE AND WHEEL ASSEMBLY REVOLVES TIMES PER SECOND OR (Z AT THE VEHICLE SPEED OF MPH KPH 4HE CALCULATED FREQUENCY OF (Z IS THE lRST ORDER TIRE AND WHEEL FREQUENCY 4HE SECOND ORDER FREQUENCY OF THE TIRE AND WHEEL ASSEMBLIES IS TWICE THIS NUMBER OR (Z X ( Z 4HE THIRD ORDER FREQUENCY IS THREE TIMES THIS NUMBER OR (Z X ( Z
6EHICLE 3PEED 6IBRATIONS $RIVE 3HAFT &REQUENCY &ORMULA +NOWING THE TIRE AND WHEEL FREQUENCY ALLOWS FOR EASY CALCULATION OF DRIVE SHAFT FREQUENCY 4HE DRIVE SHAFT DRIVES THE TIRES THROUGH THE REAR AXLE 4HEREFORE TO DETERMINE DRIVE SHAFT FREQUENCY MULTIPLY TIRE AND WHEEL FREQUENCY BY THE RATIO OF THE RING AND PINION #ALCULATE DRIVE SHAFT FREQUENCY BY PERFORMING THE FOLLOWING STEPS
4HIS RESULTS IN A DRIVE SHAFT FREQUENCY OF (Z AT THE VEHICLE SPEED OF MPH KPH 4HE CALCULATED FREQUENCY OF (Z IS THE lRST ORDER DRIVE SHAFT FREQUENCY 4HE SECOND ORDER FREQUENCY OF THE DRIVE SHAFT IS TWICE THIS NUMBER OR (Z
/BTAIN THE AXLE RATIO X
-ULTIPLY THE TIRE AND WHEEL FREQUENCY AT VIBRATION SPEED BY THE AXLE RATIO 4 I RE ( Z X ! X L E R A T I O $ RI V E S H A FT F RE Q U E N C Y &OR EXAMPLE A 02 EQUIPPED VEHICLE WITH A VIBRATION AT MPH KPH AND AN AXLE RATIO OF 5SING THIS INFORMATION MULTIPLY (Z THE TIRE AND WHEEL FREQUENCY AT MPH CALCULATED BY USING THE 4IRE AND 7HEEL &REQUENCY &ORMULA BY THE AXLE RATIO OF X ( Z
)T IS IMPORTANT TO REMEMBER THE DIFFERENCE BETWEEN DRIVE SHAFT AND AXLE SHAFT FREQUENCIES 4HE FREQUENCY OF DRIVE SHAFT CONCERNS ARE HIGH SINCE THEY ROTATE APPROXIMATELY THREE TO FOUR TIMES THAT OF THE TIRE AND WHEEL ASSEMBLIES !XLE SHAFT CONCERNS ARE LOWER FREQUENCY BECAUSE THEY ROTATE AT TIRE AND WHEEL SPEED
6EHICLE 3PEED 6IBRATIONS $RIVE 3HAFTS
$RIVELINE 6IBRATION
4HE FUNCTION OF A DRIVE SHAFT IS TO TRANSMIT POWER $RIVELINE VIBRATIONS CAN BE CAUSED BY FROM ONE POINT TO ANOTHER IN A SMOOTH ACTION s $AMAGED DRIVE SHAFTS 4HE SHAFTS ARE DESIGNED TO SEND TORQUE THROUGH s -ISSING SHAFT BALANCE WEIGHTS AN ANGLE FROM THE TRANSMISSION TRANSFER CASE ON !7$ VEHICLES TO THE AXLE s 7ORN OR OUT OF BALANCE WHEELS 5SE EXACT REPLACEMENT PARTS FOR ATTACHING THE DRIVE SHAFTS 4HIS ENSURES SAFE OPERATION 4HE SPECIlED TORQUE ALWAYS MUST BE APPLIED WHEN TIGHTENING THE FASTENERS /FTEN !UDI VEHICLES WILL HAVE SPECIAL PROCEDURES TO ALIGN THE ENGINE AND TRANSMISSION IN THE VEHICLE 4HERE ARE SPECIAL PROCEDURES TO ALIGN THE DRIVE SHAFTS AS WELL $RIVE SHAFT VIBRATIONS CAN BE CLASSIlED INTO THREE DIFFERENT ORDERS lRST ORDER SECOND ORDER AND FOURTH ORDER ! lRST ORDER VIBRATION MAY BE CAUSED BY A BENT OR OUT OF BALANCE DRIVE SHAFT CONDITION ! SECOND ORDER VIBRATION MAY BE CAUSED BY DRIVE SHAFT ANGLE 5 JOINT CANCELLATION AND WORN #6 JOINTS OR 5 JOINTS ! FOURTH ORDER VIBRATION MAY BE CAUSED BY A WORN #6 JOINT OR 5 JOINT
s ,OOSE WHEEL BOLTS s 7ORN 5 JOINTS OR CONSTANT VELOCITY JOINTS s ,OOSE OR BROKEN SPRINGS s ,OOSE PINION GEAR NUT s %XCESSIVE PINION YOKE RUNOUT )N ADDITION CHECK FOR LOOSE OR DAMAGED FRONT END COMPONENTS OR ENGINETRANSMISSION MOUNTS 4HESE COMPONENTS CAN CONTRIBUTE TO WHAT APPEARS TO BE A REAR END VIBRATION $O NOT OVERLOOK ENGINE ACCESSORIES BRACKETS AND DRIVE BELTS !LL DRIVELINE COMPONENTS SHOULD BE EXAMINED BEFORE ATTEMPTING ANY REPAIR
6EHICLE 3PEED 6IBRATIONS "ENT $RIVE 3HAFTS ! BENT DRIVE SHAFT CAN CAUSE A VIBRATION IN THE VEHICLE )F A BENT DRIVE SHAFT IS SUSPECTED PERFORM A RUNOUT CHECK ON THE DRIVE SHAFT 4HE DIAL INDICATOR MUST BE PLACED AT A DEGREE ANGLE FROM THE DRIVE SHAFT FOR ACCURATE READINGS &IRST MEASURE THE RUNOUT CLOSE TO EACH YOKE WELD AND VERIFY IT IS WITHIN THE SPECIlCATIONS IN THE SERVICE INFORMATION 4HE SECOND MEASUREMENT IS DONE IN THE CENTER OF THE DRIVE SHAFT TO VERIFY IT IS WITHIN SPECIlCATIONS )F THE RUNOUT IS NOT WITHIN THE SPECIlCATIONS THE DRIVE SHAFT MUST BE REPLACED &RONT $RIVE 3HAFTS
2EAR $RIVE 3HAFTS
6EHICLE 3PEED 6IBRATIONS 4RANSMISSION .OISE AND 6IBRATIONS 4RANSMISSION RELATED CONCERNS CAN CAUSE NOISE OR VIBRATIONS 4HE PURPOSE OF THE TRANSMISSION IS TO PROVIDE SEVERAL DIFFERENT GEAR RANGES TO IMPROVE VEHICLE TORQUE AND ACCELERATION QUALITIES 4HE DIFFERENT GEAR RANGES ROTATE AT DIFFERENT SPEEDS FROM THE TIRE AND WHEEL AND SHAFTS )F THE TRANSMISSION IS CAUSING THE NOISE AND VIBRATION IT WILL USUALLY CHANGE CHARACTERISTICS WHEN THE DIFFERENT GEAR RANGES ARE SELECTED -OST TRANSMISSION NOISES AND VIBRATION WILL NOT BE PRESENT WHEN THE TRANSMISSION IS PLACED IN NEUTRAL DURING THE ROAD TEST -ANUAL TRANSMISSIONS UTILIZE A CLUTCH ASSEMBLY BETWEEN THE ENGINE AND TRANSMISSION 4HE CLUTCH ASSEMBLY CAN CAUSE NOISE AND VIBRATION )F IT IS SUSPECTED THAT THE MANUAL TRANSMISSION IS CAUSING NOISE AND VIBRATION REFER TO THE TRANSMISSION SECTION OF THE SERVICE INFORMATION FOR DIAGNOSTIC PROCEDURES !UTOMATIC TRANSMISSIONS UTILIZE A TORQUE CONVERTER BETWEEN THE ENGINE AND TRANSMISSION 4HE TORQUE CONVERTER IS DRIVEN AT ENGINE SPEED 4ORQUE CONVERTER FREQUENCY WILL MATCH ENGINE FREQUENCY ! LOCKING TORQUE CONVERTER IMPROVES FUEL MILEAGE AND REDUCES ENGINE EMISSIONS 4HIS COMPONENT CAN CAUSE NOISE AND VIBRATION CONCERNS 4HE TORQUE CONVERTER OPERATION CAN BE MONITORED WITH A SCAN TOOL 2EFER TO SERVICE INFORMATION TO DIAGNOSE TORQUE CONVERTER CONCERNS
6EHICLE 3PEED 6IBRATIONS $IFFERENTIAL /PERATION 4HE DIFFERENTIAL GEAR SYSTEM DIVIDES THE TORQUE BETWEEN THE AXLE SHAFTS )T ALLOWS THE AXLE SHAFTS TO ROTATE AT DIFFERENT SPEEDS WHEN TURNING CORNERS -OST DIFFERENTIALS CONSIST OF A PAIR OF SIDE GEARS AND A PAIR OF PINION GEARS %ACH DIFFERENTIAL SIDE GEAR IS SPLINED TO AN OUTPUT SHAFT 4HE PINION GEARS ARE MOUNTED ON A PINION SHAFT AND ARE FREE TO ROTATE ON THE SHAFT 4HE PINION GEAR IS lTTED IN A BORE IN THE DIFFERENTIAL CASE AND IS POSITIONED AT A RIGHT ANGLE TO THE AXLE SHAFTS )N OPERATION POWER mOW OCCURS AS FOLLOWS s 4HE PINION GEAR ROTATES THE RING GEAR s 4HE RING GEAR BOLTED TO THE DIFFERENTIAL CASE ROTATES THE CASE s )N STRAIGHT AHEAD DRIVING THE DIFFERENTIAL CASE ROTATES AS ONE COMPLETE UNIT NO DIFFERENTIAL GEARS PINION OR SIDE GEARS ROTATE AND TRANSMIT POWER TO THE OUTPUT SHAFTS s 7HEN CORNERING THE DIFFERENTIAL PINION GEARS MOUNTED ON THE PINION SHAFT IN THE CASE ROTATE THE SIDE GEARS AT A DIFFERENCE IN SPEED ALLOWING THE TIRES TO ROTATE SMOOTHLY s 4HE SIDE GEARS SPLINED TO THE OUTPUT SHAFTS ROTATE THE SHAFTS DURING STRAIGHT AHEAD DRIVING OR CORNERING
3TRAIGHT !HEAD $RIVING $URING STRAIGHT AHEAD DRIVING THE DIFFERENTIAL PINION GEARS DO NOT ROTATE ON THE DIFFERENTIAL PINION SHAFT BECAUSE INPUT TORQUE APPLIED TO THE GEARS IS DIVIDED AND DISTRIBUTED EQUALLY BETWEEN THE TWO SIDE GEARS !S A RESULT THE PINION GEARS REVOLVE WITH THE DIFFERENTIAL PINION SHAFT BUT DO NOT ROTATE AROUND IT 4URNING #ORNERS 4HE OUTSIDE WHEEL MUST TRAVEL A GREATER DISTANCE THAN THE INSIDE WHEEL IN ORDER TO COMPLETE A TURN 4HE DIFFERENCE MUST BE COMPENSATED FOR TO PREVENT THE TIRES FROM SCUFlNG AND SKIDDING THROUGH TURNS 4HE DIFFERENTIAL ALLOWS THE AXLE SHAFTS TO TURN AT UNEQUAL SPEEDS )N THIS INSTANCE THE INPUT TORQUE APPLIED TO THE PINION GEARS IS NOT DIVIDED EQUALLY 4HE PINION GEARS NOW ROTATE AROUND THE PINION MATE SHAFT IN OPPOSITE DIRECTIONS 4HIS ALLOWS THE SIDE GEAR AND AXLE SHAFT ATTACHED TO THE OUTSIDE WHEEL TO ROTATE AT A FASTER SPEED )F A NOISE OR VIBRATION IS BEING CAUSED BY THE DIFFERENTIAL THE CONCERN WILL USUALLY CHANGE CHARACTERISTICS DURING STRAIGHT AHEAD DRIVING AND WHEN TURNING CORNERS 4HIS IS DUE TO THE DIFFERENT OPERATION OF THE DIFFERENTIAL WHEN TURNING $IFFERENTIAL NOISES ARE OFTEN TORQUE SENSITIVE RESULTING IN CHARACTERISTIC CHANGES WHEN CHANGING TORQUE INPUT $URING A ROAD TEST DRIVE IN A lGURE PATTERN IN A SAFE AND OPEN AREA AND DETERMINE IF THE .6( CONCERN IS MORE PRONOUNCED WHILE LOADING THE DIFFERENTIAL GEARS #ONSULT THE AXLE SECTION OF SERVICE INFORMATION IF IT IS SUSPECTED THE DIFFERENTIAL IS CAUSING A NOISE OR VIBRATION CONCERN
6EHICLE 3PEED 6IBRATIONS "EARING .OISE
'EAR .OISE
7HEEL BEARINGS AND PINION AND DIFFERENTIAL GEAR BEARINGS CAN PRODUCE NOISE WHEN WORN OR DAMAGED "EARING NOISE CAN BE EITHER A WHINING OR A GROWLING SOUND
'EAR NOISE USUALLY OCCURS AT SPECIlC SPEED RANGES USUALLY BETWEEN AND MPH AND KPH OR ABOVE MPH KPH 'EAR NOISE CAN ALSO OCCUR DURING SPECIlC DRIVING CONDITIONS SUCH AS ACCELERATION DECELERATION COAST OR CONSTANT LOAD 'EAR NOISES USUALLY DISAPPEAR IF THE VEHICLE IS ALLOWED TO COAST WITHOUT ANY ACCELERATION OR DECELERATION TORQUE APPLIED TO THE GEARS
&AULTY WHEEL BEARINGS PRODUCE NOISE THAT GENERALLY CHANGES WHEN THE BEARINGS ARE LOADED 7HEN ROAD TESTING THE VEHICLE TURN THE VEHICLE SHARPLY TO THE LEFT AND RIGHT 4HIS LOADS THE BEARINGS AND CHANGES THE NOISE LEVEL 7HEN WHEEL BEARING DAMAGE IS SLIGHT THE NOISE IS USUALLY NOT NOTICEABLE AT SPEEDS ABOVE MPH KPH
$RIVELINE 3NAP
0INION BEARINGS USUALLY CHANGE NOISE CHARACTERISTICS WHEN TORQUE INPUT IS CHANGED IE ! SNAP OR CLUNK NOISE WHEN THE VEHICLE IS SHIFTED INTO GEAR OR THE CLUTCH IS ENGAGED CAN COASTING OR HARD ACCELERATIONS BE CAUSED BY s (IGH ENGINE IDLE SPEED s ,OOSE ENGINETRANSMISSIONTRANSFER CASE MOUNTS 7HEEL "EARING
s 7ORN 5 JOINTS s ,OOSE AXLE MOUNTS s ,OOSE PINION GEAR NUT AND YOKE s %XCESSIVE RING GEAR BACKLASH s %XCESSIVE SIDE GEARCASE CLEARANCE
!XLE 3HAFT 7HEEL (UB
4HE SOURCE OF A SNAP OR CLUNKING NOISE CAN BE DETERMINED BY RAISING THE VEHICLE ON A HOIST WITH THE WHEELS FREE TO ROTATE (AVE ANOTHER TECHNICIAN SHIFT THE TRANSMISSION INTO GEAR AND LISTEN FOR THE NOISE ! STETHOSCOPE EITHER MANUAL OR ELECTRONIC IS HELPFUL IN ISOLATING THE SOURCE OF THE NOISE 5SE CAUTION WHEN WORKING AROUND ROTATING COMPONENTS
6EHICLE 3PEED 6IBRATIONS 3USPENSION #OMPONENTS 4HE SUSPENSION SYSTEM PLAYS A LARGE ROLE IN THE EFFECTS OF .6( ON A VEHICLE 3IMILAR TO THE STEERING SYSTEM COMPONENTS THE SUSPENSION OF A VEHICLE CAN EASILY ACT AS THE MEDIUM THROUGH WHICH VIBRATION CAN BE TRANSFERRED 7HEN THE SOURCE OF AN .6( CONCERN IS DETERMINED YOU USUALLY CAN lND THE CAUSE BY PERFORMING A THOROUGH VISUAL INSPECTION 0ASSENGERS OF A VEHICLE ARE SENSITIVE TO THE EFFECTS OF A HARSH RIDING SUSPENSION &OR THIS REASON VARIOUS MEASURES ARE TAKEN IN THE DESIGN AND DEVELOPMENT PHASE OF A VEHICLES SUSPENSION &OR EXAMPLE SPRINGS AND BUSHINGS ARE CAREFULLY SELECTED TO PROVIDE A SMOOTH RIDE AND ALSO TO REDUCE THE IMPACT OF STEERING FORCES 4HE VIBRATION OF A VEHICLES SUSPENSION SYSTEM CONSISTS OF VERTICAL AND LONGITUDINAL FORCES 4HE VERTICAL FORCES ARE CONTROLLED BY WELL PROPORTIONED SPRUNG AND UNSPRUNG WEIGHTS SHOCKS AND COIL SPRINGS
"USHINGS ARE DESIGNED SO THEY ARE SOFTER IN ONE AREA THAN IN ANOTHER "USHINGS ARE MADE SOFTER IN THE LONGITUDINAL DIRECTION SO THE EFFECTS OF TIRE IMPACT OR ROAD SHOCK ARE REDUCED "USHINGS ARE MADE STIFFER IN THE LATERAL DIRECTION SO STEERING THE VEHICLE DOES NOT HAVE AS MUCH OF AN ADVERSE EFFECT )T IS IMPORTANT THAT BUSHINGS AND INSULATORS ARE IN GOOD CONDITION AND THEY ARE OF THE SPECIlED TYPE IN ORDER TO AVOID .6( CONCERNS IN THE SUSPENSION .OISE FROM THE SUSPENSION IS TYPICALLY CAUSED BY ONE OF THE FOLLOWING s ,OOSE COMPONENTS s 7ORN BUSHINGS s 0OOR LUBRICATION
,ONGITUDINAL FORCES ARE CONTROLLED BY CAREFUL SELECTION OF SUSPENSION BUSHINGS 4HE SUSPENSION OF A PARTICULAR VEHICLE IS DESIGNED SO THAT THE LOWER CONTROL ARMS ABSORB LONGITUDINAL IMPACTS FROM THE TIRES 4IRE IMPACT IS FURTHER DAMPENED BY BUSHINGS BEFORE BEING TRANSMITTED THROUGH THE CROSSMEMBER TO THE BODY 4HIS LONGITUDINAL COMPLIANCE DEPENDS ON THE SPRING CONSTANT RATE OF THE RUBBER INSULATOR BUSHINGS
6EHICLE 3PEED 6IBRATIONS 3TEERING #OMPONENTS -ANY CUSTOMER CONCERNS REGARDING .6( ARE RELATED TO THE STEERING SYSTEM 4HIS IS BECAUSE THE DRIVER IS HOLDING THE STEERING WHEEL AT ALL TIMES WHILE DRIVING AND ANY VIBRATIONS FROM THE TIRES OR SUSPENSION ARE TRANSFERRED TO THE STEERING COMPONENTS .OISE RELATED CONCERNS ARE USUALLY GENERATED WITHIN THE STEERING SYSTEM ITSELF 6IBRATION RELATED CONCERNS CAN BE CAUSED BY MANY DIFFERENT COMPONENTS INCLUDING COMPONENTS IN THE SUSPENSION TIRES AND WHEELS .OISE 3OME STEERING SYSTEM SOUNDS ARE NORMAL AND SHOULD NOT BE OF CONCERN 4HERE ARE SOME INHERENT NOISES IN ALL POWER STEERING SYSTEMS (OWEVER OTHER SOUNDS MAY INDICATE A PROBLEM WITHIN THE STEERING SYSTEM -ANY NORMAL STEERING SYSTEM SOUNDS ARE RELATED TO THE POWER STEERING PUMP (ISSING AND RATTLING ARE TWO STEERING SYSTEM RELATED NOISES THAT MAY OCCUR
(ISS ! HISSING NOISE USUALLY ORIGINATES IN THE STEERING GEARBOX AND POWER STEERING PUMP 7ITH THE VEHICLE STATIONARY A HISSING SOUND MAY BE HEARD WHEN THE STEERING WHEEL IS TURNED WHICH RESULTS FROM mUID PRESSURE PULSATION IN THE PUMP 7HEN DIAGNOSING A HISSING NOISE CONCERN lRST INSPECT ALL STEERING HOSES TO ENSURE THEY ARE NOT TOUCHING OTHER PARTS OF THE VEHICLE #HECK SERVICE INFORMATION AND TECHNICAL SERVICE BULLETINS FOR POSSIBLE UPDATED HOSES OR HOSE ROUTINGS WHEN DIAGNOSING A HISSING CONCERN 2ATTLE 2ATTLE USUALLY ORIGINATES IN THE STEERING GEAR 4HE POSSIBLE CAUSES FOR THIS CONDITION ARE s 7ORN STEERING OR SUSPENSION COMPONENTS s 7ORN OR DAMAGED RACK AND PINION RETAINERS AND BUSHINGS s 0RESSURE HOSES TOUCHING OTHER VEHICLE COMPONENTS
4OOLS 3IROMETER 6IBRATACH 4HE SIROMETER IS A TOOL THAT IS USEFUL WHEN DIAGNOSING .6( CONCERNS /RIGINALLY USED FOR READING SMALL ENGINE RPM THIS INEXPENSIVE TOOL IS HIGHLY ACCURATE FOR MEASURING VIBRATION FREQUENCIES 4HE SIROMETER HAS ENOUGH RANGE TO MEASURE THE MAJORITY IF NOT ALL OF AN AUTOMOBILES VIBRATION FREQUENCIES 4HE TOOL CAN BE PURCHASED AT MOST FULL SERVICE SMALL ENGINE REPAIR AND PARTS CENTERS 4HE SIROMETER HAS A WIRE THAT WHEN ADJUSTED TO THE PROPER LENGTH RESONATES TO THE VIBRATION FREQUENCY 4O USE THE SIROMETER HOLD IT AGAINST A VIBRATING COMPONENT 2OTATE THE DIAL TO EXTEND THE WIRE AND CHANGE THE WIRES RESONANT FREQUENCY UNTIL THE WIRE VIBRATES AT ITS WIDEST ARC 4HEN READ THE FREQUENCY ON THE TOOLS FACE LABELED #YCLES 0ER 3ECOND n (ERTZ !LWAYS ADJUST THE LENGTH OF THE WIRE FROM ITS SMALLEST LENGTH TO ITS LONGEST LENGTH TO ENSURE ALL FREQUENCIES ARE BEING RECORDED )T IS POSSIBLE TO HAVE MORE THAN ONE VIBRATION PRESENT IN A VEHICLE
4OOLS %6! ))£ 4HE %6! )) ALLOWS FOR A SYSTEMATIC COLLECTION OF INFORMATION THAT IS NECESSARY TO ACCURATELY DIAGNOSE AND REPAIR .6( PROBLEMS 4HE PROPER USE OF THE %6! )) CAN SIGNIlCANTLY REDUCE VEHICLE SERVICE TIME 4HE TOOL USES AN ELECTRONIC PICK UP THAT MEASURES VIBRATION FREQUENCY AND AMPLITUDE !N ADDITIONAL PICK UP CAN BE ADDED AND TWO SOURCES OF VIBRATIONS CAN BE COMPARED 4HE PICK UPS CAN BE PLACED ANYWHERE ON THE VEHICLE "Y PLACING THE PICK UP ON DIFFERENT AREAS OF THE VEHICLE AND COMPARING THE VIBRATIONS AMPLITUDE AS DISPLAYED ON THE SCREEN THE SOURCE OF THE VIBRATION CAN BE LOCATED BY THE HIGHEST AMPLITUDE )F THE STEERING WHEEL OR PASSENGERS SEAT IS VIBRATING THE PICK UP CAN BE PLACED THERE TO MEASURE THE VIBRATION
4HE %6! )) CONTAINS A SOFTWARE DATABASE THAT CONTAINS MOST TIRE SIZES AND AXLE GEAR RATIOS 7HEN THE CORRECT VEHICLE INFORMATION IS ENTERED INTO THE %6! )) THE TOOL WILL DETERMINE AND DISPLAY THE SOURCES OF THE VIBRATION 4HIS FEATURE ELIMINATES MOST OF THE MATHEMATICAL FORMULAS AND CALCULATES THE KNOWN FREQUENCIES OF ROTATING COMPONENTS 4HE %6! )) CAN RECORD SNAPSHOTS DURING A ROAD TEST AND THE DATA REPLAYED TO DETERMINE THE VIBRATION FREQUENCY 4HIS IS USEFUL FOR INTERMITTENT OR SHORT DURATION VIBRATIONS 4HE %6! )) HAS FEATURE TO USE AN INDUCTIVE PICK UP TIMING LIGHT TO VISUALLY mASH A VIBRATION FREQUENCY 4HE OPERATION MANUAL FOR THE TOOL DESCRIBES HOW TO USE THIS FEATURE TO HELP IN DIAGNOSING THE LOCATION OF A VIBRATIONS SOURCE 4HE mASHING TIMING LIGHT CAN BE USED TO BALANCE PROPELLER SHAFTS #ONTACT %QUIPMENT 3OLUTIONS FOR MORE INFORMATION ON THE %6! ))
4OOLS #HASSIS%!2£ 4HE #HASSIS%!2 IS A VERSATILE ELECTRONIC LISTENING TOOL THAT ALLOWS THE USER TO LISTEN TO AMPLIlED SOUNDS THROUGH A PROFESSIONAL SET OF HEADPHONES 4HE PROPER USE OF THE #HASSIS%!2 CAN REDUCE THE TIME IN DIAGNOSING .6( CONCERNS ON A VEHICLE 4HE TOOL HAS MULTIPLE MICROPHONE INPUTS THAT CAN BE PLACED IN DIFFERENT SECTIONS OF THE VEHICLE !TTACHMENT OF THE SIX MICROPHONES AND CLAMPS HELPS TO LOCATE MANY DIFlCULT TO DIAGNOSE VEHICLE PARTS $URING A ROAD TEST THESE PARTS DO NOT MAKE THE SAME SOUNDS AS WHEN THE CAR IS ON A HOIST 4O ACCURATELY DIAGNOSE AN UNDER VEHICLE PROBLEM OPERATE THE VEHICLE SO ALL PARTS AND BEARINGS ARE UNDER FULL LOAD 4HE DIFFERENT INPUTS ALLOW THE LOUDEST AREA TO BE DETERMINED AND THUS DETERMINE THE POSSIBLE SOURCE 0LACE THE MICROPHONES ON PARTS OR AREAS SUSPECTED AS BEING THE POSSIBLE SOURCE 3OME OF THESE VEHICLE PARTS AND AREAS INCLUDE
2EMEMBER THAT NOISES CAN BE CAUSED FROM A VIBRATION THAT RESONATES THROUGH ANOTHER COMPONENT CAUSING IT TO VIBRATE !LWAYS CHECK FOR A VIBRATION FREQUENCY WHEN BEGINNING TO DIAGNOSE A NOISE CONCERN #ONTACT %QUIPMENT 3OLUTIONS FOR MORE INFORMATION ON THE #HASSIS%!2
s 7HEEL BEARINGS s "RAKE CALIPERS s #6 JOINTS s ,EAF AND COIL SPRINGS s $IFFERENTIAL s 4RANSMISSION s "ODY SQUEAKS AND RATTLES s 5NDER DASH s &UEL INJECTORS s 'ENERATOR s 7ATER PUMP s 3MOG PUMP s 0OWER STEERING PUMP s !IR CONDITIONING COMPRESSORS
4OOLS /THER 4OOLS 3EVERAL AUTOMOTIVE TOOL MANUFACTURERS HAVE DEVELOPED ELECTRONIC TOOLS FOR MEASURING AND RECORDING NOISES AND VIBRATIONS 3OME OF THESE TOOLS HAVE MULTIPLE VIBRATION AND NOISE INPUTS RECORDING AND GRAPHING CAPABILITIES .OT ALL OF THE TOOLS AVAILABLE HAVE BEEN COVERED 0LEASE CONTACT AUTOMOTIVE TOOL MANUFACTURERS TO REQUEST INFORMATION
'LOSSARY .6( 4ERMINOLOGY !UDIBLE 2ANGE OF 3OUND n 3OUNDS THAT ARE IN THE RANGE OF TO (ERTZ (Z
&REQUENCY n 4HE NUMBER OF COMPLETE CYCLES THAT OCCURS IN A GIVEN PERIOD OF TIME
!MPLITUDE n 4HE VERTICAL MEASUREMENT BETWEEN THE TOP AND BOTTOM OF A WAVE !LSO SEE MAGNITUDE
(ARSHNESS n !N AGGRESSIVE SUSPENSION FEEL OR LACK OF GIVE IN RESPONSE TO A SINGLE INPUT
"EAT n !N .6( CONCERN PRODUCED BY TWO SOUNDS THAT IS MOST NOTICEABLE WHEN THE FREQUENCY DIFFERENCE IS TO (Z "EAD 3EATING n 4HE PROCESS OF SEATING THE TIRE TO THE RIM )F PROPERLY LUBRICATED THE BEAD SEATING OCCURS WHEN THE TIRE AND WHEEL ARE ASSEMBLED #OMPELLING &ORCE n ! VIBRATING OBJECT ACTING UPON ANOTHER OBJECT THAT CAUSES THE OTHER OBJECT TO VIBRATE
(ERTZ n 4HE UNIT OF FREQUENCY MEASUREMENT IN SECONDS A VIBRATION OCCURRING TIMES PER SECOND WOULD BE AN (Z VIBRATION )NTENSITY n 4HE PHYSICAL QUALITY OF SOUND THAT RELATES TO THE AMOUNT AND DIRECTION OF THE mOW OF ACOUSTIC ENERGY AT A GIVEN SPEED ,ATERAL 2UNOUT n ! CONDITION WHERE A ROTATING COMPONENT DOES NOT ROTATE IN A TRUE PLANE 4HE COMPONENT MOVES SIDE TO SIDE WOBBLES ON ITS ROTATIONAL AXIS
-AGNITUDE !MPLITUDE n 4HE AMOUNT OF FORCE #YCLE n 4HE PATH A WAVE TRAVELS BEFORE THE WAVE OR THE INTENSITY OF THE VIBRATION 4HE MAGNITUDE BEGINS TO REPEAT THE PATH AGAIN OR STRENGTH OF A VIBRATION IS ALWAYS GREATEST AT THE POINT OF RESONANCE $AMPEN n 4O REDUCE THE MAGNITUDE OF A NOISE OR VIBRATION $AMPERS n ! COMPONENT USED TO DAMPEN A NOISE OR VIBRATION &OAM AND RUBBER ARE COMMONLY USED TO DAMPEN VIBRATIONS
-EDIUM n 0ROVIDES A PATH FOR SOUND WAVES TO TRAVEL THROUGH
.ATURAL &REQUENCY n 4HE FREQUENCY THAT A COMPONENT WILL VIBRATE THE EASIEST .ORMALLY $YNAMIC "ALANCE n ! PROCEDURE THAT BALANCES A THE LARGER THE MASS THE LOWER ITS NATURAL TIRE AND WHEEL ASSEMBLY IN TWO PLANES $YNAMIC FREQUENCY BALANCE REMOVES RADIAL AND LATERAL VIBRATIONS s %NGINE BLOCK (Z s 4IRE AND WHEEL ASSEMBLIES (Z n $RONING (IGH 3PEED n ! LONG DURATION NON PROPORTIONAL TO VEHICLE SPEED DIRECTIONAL HUMMING NOISE THAT IS UNCOMFORTABLE s 3USPENSION (Z TO THE EARS AND HAS A RANGE OF MPH KPH s $RIVELINE (Z AND UP s $IFFERENTIAL COMPONENTS (Z $RONING ,OW 3PEED n ! LONG DURATION LOW PITCHED NOISE THAT IS NON DIRECTIONAL AND HAS A .OISE n 4HE UNPLEASANT OR UNEXPECTED SOUND RANGE OF UP TO MPH KPH CREATED BY A VIBRATING OBJECT $RONING -IDDLE 3PEED n ! LONG DURATION LOW /RDER n 4HE NUMBER OF DISTURBANCES CREATED IN PITCHED NOISE THAT IS NON DIRECTIONAL AND HAS A ONE REVOLUTION OF A COMPONENT RANGE OF TO MPH TO KPH 0HASE n 4HE POSITION OF A VIBRATION CYCLE RELATIVE %LECTRONIC 6IBRATION !NALYZER )) %6! )) n !N TO ANOTHER VIBRATION CYCLE IN THE SAME HERTZ RATE ELECTRONIC .6( DIAGNOSTIC TOOL THAT MEASURES TIME FRAME FREQUENCY AND AMPLITUDE
'LOSSARY 0HASE n 4HE CYCLE PATTERN OF TWO OR MORE VIBRATIONS THAT OVERLAP AND COMBINE TO INCREASE OR DECREASE THE OVERALL MAGNITUDE
3TATIC "ALANCE n 4HE METHOD OF BALANCING A TIRE AND WHEEL ASSEMBLY IN A SINGLE PLANE 3TATIC BALANCING REMOVES ONLY THE LATERAL SIDE TO 0ITCH n 4HE PHYSICAL QUALITY OF SOUND THAT RELATES SIDE WOBBLE IMBALANCE AND THE TIRE AND WHEEL ASSEMBLY COULD POSSIBLY HAVE A RADIAL UP AND TO THE FREQUENCY OF THE WAVE DOWN VIBRATION 2ADIAL &ORCE 6ARIATION 2&6 n ! MEASUREMENT 4ORQUE 3ENSITIVE 6IBRATION OR .OISE n ! OF THE TIRES UNIFORMITY UNDER LOAD IN REGARDS VIBRATION OR NOISE THAT IS SENSITIVE TO DIFFERENT TO THE VARIATION OF THE LOAD ACTING TOWARDS THE LOADS AND TORQUE APPLIED TO THE DRIVE TRAIN OF A CENTER OF THE TIRE COMMONLY REFERRED TO AS THE VEHICLE 4HE VIBRATION OR NOISE CHANGES WHEN THE TIREgS SIDEWALL VARIATION THROTTLE POSITION OR TRANSMISSION GEARING IS USED 2ADIAL 2UNOUT n ! CONDITION WHERE A ROTATING DURING A ROAD TEST TO CHANGE THE TORQUE APPLIED COMPONENT DOES NOT ROTATE IN A TRUE PLANE 4HE TO THE DRIVE TRAIN COMPONENT MOVES UP AND DOWN ON ITS ROTATIONAL 6IBRATION n 4HE REPETITIVE MOTION OF AN OBJECT AXIS BACK AND FORTH OR UP AND DOWN WHICH MAY BE 2ESONANCE n 4HE TENDENCY OF A SYSTEM TO FELT OR HEARD RESPOND INCREASINGLY TO A COMPELLING FORCE 7HEEL $IAMETER n 4HE DIMENSION OF A WHEEL OSCILLATING AT OR NEAR THE NATURAL FREQUENCY OF MEASURED ON THE INSIDE OF THE WHEEL AT THE THE SYSTEM 4HIS CAUSES A SUDDEN AND LARGE BEAD SEAT AREA VIBRATION 2OAD .OISE n ! NOISE THAT OCCURS WHILE DRIVING ON GRAVEL OR ROUGHLY PAVED ROADS AT ALL VEHICLE SPEEDS OR WHEN A VEHICLE IS COASTING 3HAKE ,ATERAL n ! SIDE TO SIDE VIBRATION OF THE BODY SEATS AND STEERING WHEEL 3HAKE 6ERTICAL n !N UP AND DOWN VIBRATION OF THE BODY SEATS AND STEERING WHEEL 3HIMMY (IGH 3PEED n ! VIBRATION THAT CAUSES THE STEERING WHEEL TO OSCILLATE WHEN DRIVING ON SMOOTH ROADS AT HIGH SPEEDS 3HIMMY ,OW 3PEED n ! VIBRATION THAT CAUSES THE STEERING WHEEL TO OSCILLATE WHEN DRIVING ACROSS A BUMP AT LOW SPEEDS 3OURCE #OMPONENT n 4HE COMPONENT THAT IS DIAGNOSED AS BEING THE ROOT CAUSE OF A VIBRATION OR NOISE CONCERN 3OUND n 4HE RESULT OF A VIBRATING DISTURBANCE OF AN OBJECT WHICH PRODUCES WAVES THAT TRANSMIT OUT FROM THE SOURCE
#ONCERN DISAPPEARS OR IS DIMINISHED AFTER THE CAR HAS BEEN DRIVEN AWHILE
#HECK TIRES FOR 4EMPORARY &LAT 3POTTING 4IRES CAN BECOME TEMPORARY FLAT SPOTTED WHEN A VEHICLE HAS BEEN DRIVEN AND THEN PARKED ON A COLD SURFACE 4HIS MAY HAPPEN IN COLD CLIMATES AS WELL AS WARM CLIMATES 6EHICLES PARKED FOR LONG PERIODS OF TIME ANDOR STORED WITH LOW AIR PRESSURE ARE ALSO SUSCEPTIBLE TO FLAT SPOTTING
&ELT WHILE BRAKING
#HECK s "RAKE COMPONENTS s 3TEERING COMPONENTS s 3USPENSION COMPONENTS s 2ELEVANT 4ECHNICAL "ULLETINS
огромный архив документации по автомобилям Volkswagen, Skoda, Seat, Audi
Volkswagen Technical Site: http://vwts.ru http://vwts.info #HECK DRIVE TRAIN FOR s 0ROP SHAFT MISALIGNMENT s $AMAGED AXLE SHAFTS#6 JOINTS s 7ORN WHEEL BEARINGS s 2EAR DIFFERENTIAL PERFORMANCE
#HECK TIRES FOR s (IGH 2ADIAL &ORCE 6ARIATION 2&6 s )MBALANCE s )RREGULAR WEAR s !BNORMAL PRESSURE
#HECK WHEELS FOR s $IRT MUD SNOW OR ICE BUILD UP s $AMAGE s -ISSING OR EXCESSIVE WHEEL WEIGHTS s ,OOSE WHEEL BOLTS s 0ROPER WHEEL TORQUE s %XCESSIVE RUNOUT
6IBRATION IS FELT AT A CERTAIN VEHICLE SPEED
#HECK #HASSIS FOR s $AMAGED OR MISALIGNED ENGINE AND TRANSMISSION MOUNTS s 0ROPER %LECTRO (YDRAULIC MOUNT OPERATION s $AMAGED OR MISALIGNED EXHAUST SYSTEM AND COMPONENTS
#HECK %NGINE FOR s -ISFIRES s !CCESSORY VIBRATIONS s #AMSHAFT CRANKSHAFT AND INTERMEDIATE SHAFT IMBALANCE
#HECK DRIVE TRAIN FOR s 0ROP SHAFT MISALIGNMENT s $AMAGED AXLE SHAFTS s $AMAGED #6 JOINTS s 2EAR DIFFERENTIAL PERFORMANCE s 0ROPER TORQUE CONVERTER PERFORMANCE
6IBRATION IS FELT AT A CERTAIN ENGINE SPEED
)S IT FELT THROUGH SEATVEHICLE FLOOR PAN n 3TART WITH REAR AXLE
$IAGNOSE ACCORDING TO CONDITIONS LISTED BELOW
)S IT FELT THROUGH THE STEERING WHEEL n 3TART WITH FRONT AXLE
2OAD TEST TO VERIFY CONCERN
#HECK VEHICLE HISTORY PRIOR TO DIAGNOSIS AND USE .6( 330 FOR IN DEPTH DIAGNOSIS
$IAGNOSTIC &LOW #HART
Vorsprung durch Technik
All rights reserved. Technical specifications subject to change without notice. Audi Australia
Noise Vibration and Harshness
Self Study Programme NVH
4ABLE OF #ONTENTS #OURSE 'OALS )NTRODUCTION 4HEORY #HARACTERISTICS OF .OISE 6IBRATION AND (ARSHNESS .6( 'ENERATION OF .OISE AND 6IBRATION 3OUND AND 3OUND 7AVES !UDIBLE 2ANGE OF 3OUND .6( 4ERMINOLOGY 4YPES OF .OISE #OMPELLING &ORCE AND 6IBRATING "ODY 6IBRATION 6IBRATION 4RANSFER 0ATH 6IBRATION /RDER 4YPES OF 6IBRATION 2IDE #OMFORT
$IAGNOSIS 'ETTING 'OOD )NFORMATION FROM 3ERVICE !DVISORS 4HE &OUR 3TEPS $IAGNOSING AND 3OLVING #USTOMER #ONCERNS /THER )NFORMATION 3OURCES 0RE 2OAD 4EST )NSPECTION 2OAD 4EST 4IPS 2OAD 4ESTING
%NGINE 6IBRATIONS %NGINE 3PEED 2ELATED 6IBRATIONS 4YPES OF %NGINE 6IBRATIONS %NGINE 6IBRATION &ORMULA %NGINE !CCESSORY &ORMULA 4YPES OF %NGINE .OISE %XHAUST .OISE %NGINE &IRING &REQUENCY &ORMULA
6EHICLE 3PEED 6IBRATIONS 4IRES AND 7HEELS 4IRE 6IBRATION &ORMULAS $RIVE 3HAFT &REQUENCY &ORMULA $RIVE AND !XLE 3HAFTS $RIVELINE 6IBRATION 4RANSMISSION .OISE AND 6IBRATIONS $IFFERENTIAL /PERATION $RIVELINE 3NAP 3USPENSION #OMPONENTS 3TEERING #OMPONENTS .EW
4OOLS 3IROMETER %6! )) #HASSIS%!2 /THER 4OOLS
'LOSSARY .6( 4ERMINOLOGY
$IAGNOSTIC &LOW #HART +NOWLEDGE !SSESSMENT )MPORTANT.OTE 4HE 3ELF 3TUDY 0ROGRAM PROVIDES YOU WITH INFORMATION REGARDING DESIGNS AND FUNCTIONS 4HE 3ELF 3TUDY 0ROGRAM IS NOT A REPAIR MANUAL &OR MAINTENANCE AND REPAIR WORK ALWAYS REFER TO THE CURRENT TECHNICAL LITERATURE
Volkswagen Technical Site: http://vwts.ru http://vwts.info огромный архив документации по автомобилям Volkswagen, Skoda, Seat, Audi
I
#OURSE 'OALS
#OURSE 'OALS 4HIS COURSE WILL ENABLE YOU TO s )DENTIFY THE TERMINOLOGY USED IN DIAGNOSING .OISE 6IBRATION AND (ARSHNESS .6( CONCERNS s )DENTIFY THE DIFFERENT TYPES OF .6( s )DENTIFY THE STEPS OF THE .6( SYSTEMATIC DIAGNOSTIC APPROACH s )DENTIFY THE ROAD TEST PROCEDURES NECESSARY TO ISOLATE A NOISE OR VIBRATION s #ALCULATE .6( FREQUENCIES NECESSARY FOR COMPONENT CLASSIlCATION s )DENTIFY TEST EQUIPMENT AND TOOLS USED IN DIAGNOSING AND CORRECTING .6( CONCERNS s )DENTIFY DIAGNOSE AND SPECIFY THE COMPONENT CAUSING THE .6( CONCERN
)NTRODUCTION )NTRODUCTION 4HIS 3ELF 3TUDY 0ROGRAM FOCUSES ON VEHICLE .OISE 6IBRATION AND (ARSHNESS .6( THEIR CAUSES AND DIAGNOSTIC AND SERVICE PROCEDURES TO LOCATE AND CORRECT .6( CONCERNS -ODERN CARS AND TRUCKS USE A COMBINATION OF SYSTEMS TO PROVIDE THE DRIVER WITH THE SAFEST MOST RESPONSIVE AND COMFORTABLE VEHICLE EVER BUILT 4ODAYS DRIVER HAS COME TO EXPECT A SMOOTH AND QUIET RIDE IN ALL OPERATING ENVIRONMENTS 7HEN VEHICLE NOISE VIBRATION OR RIDE HARSHNESS EXCEEDS THE DRIVERS EXPECTATIONS IT IS UP TO THE TECHNICIAN TO CORRECT THE CAUSE OF THE CUSTOMERS CONCERN 6EHICLE COMPONENTS ARE BEING MANUFACTURED USING LIGHTER WEIGHT METALS ,IGHTER WEIGHT METALS REDUCE THE OVERALL VEHICLE WEIGHT THAT REDUCE EMISSIONS AND IMPROVE FUEL ECONOMY !S TECHNOLOGIES DEVELOP STRONGER AND MORE LIGHTWEIGHT METALS THIS TREND WILL CONTINUE ,IGHTER VEHICLE COMPONENTS DO NOT ABSORB NOISES AND VIBRATIONS AS WELL AS HEAVIER COMPONENTS 4HIS LEADS TO AN INCREASE IN .6( CONCERNS $IAGNOSING .6( CONCERNS HAS BEEN DEVELOPED INTO A LOGICAL AND ALMOST SCIENTIlC PROCEDURE 4HIS COURSE WILL PROVIDE THE !UDI TECHNICIAN WITH CONCEPTS TO HELP UNDERSTAND AND DIAGNOSE .6( CONCERNS
4HEORY #HARACTERISTICS OF .OISE 6IBRATION (ARSHNESS .OISE IS DElNED AS ANY UNPLEASANT OR UNEXPECTED SOUND CREATED BY A VIBRATING OBJECT 6IBRATION IS DElNED AS ANY OBJECTIONABLE REPETITIVE MOTION OF AN OBJECT BACK AND FORTH OR UP AND DOWN (ARSHNESS IS DElNED AS AN AGGRESSIVE SUSPENSION FEEL OR LACK OF hGIVEv IN RESPONSE TO A SINGLE INPUT
'ENERATION OF .OISE AND 6IBRATION ! VIBRATING OBJECT NORMALLY PRODUCES SOUND AND THAT SOUND MAY BE AN ANNOYING NOISE )N THE CASE WHERE A VIBRATING BODY IS THE DIRECT SOURCE OF NOISE SUCH AS COMBUSTION CAUSING THE ENGINE TO VIBRATE THE VIBRATING BODY OR SOURCE IS EASY TO lND )N OTHER CASES THE VIBRATING BODY MAY GENERATE A SMALL VIBRATION ONLY 4HIS SMALL VIBRATION MAY CAUSE A LARGER VIBRATION OR NOISE DUE TO THE VIBRATING BODYS CONTACT WITH OTHER PARTS 7HEN THIS HAPPENS ATTENTION FOCUSES ON WHERE THE LARGE VIBRATION OR NOISE OCCURS WHILE THE REAL SOURCE OFTEN ESCAPES NOTICE !N UNDERSTANDING OF NOISE AND VIBRATION GENERATION ASSISTS WITH THE TROUBLESHOOTING PROCESS 4HE DEVELOPMENT OF A SMALL NOISE INTO A LARGER NOISE BEGINS WHEN A VIBRATION SOURCE COMPELLING FORCE GENERATES A VIBRATION 2ESONANCE AMPLIlES THE VIBRATION WITH OTHER VEHICLE PARTS 4HE VIBRATING BODY SOUND GENERATING BODY THEN RECEIVES TRANSMISSION OF THE AMPLIlED VIBRATION
4HEORY 3OUNDS AND 3OUND 7AVES !UDIBLE 2ANGE OF 3OUND ! SOUND WAVES CYCLE PERIOD FREQUENCY AND AMPLITUDE DETERMINE THE PHYSICAL QUALITIES OF THE &OR SOUND TO BE HEARD THE RESULTING ACOUSTIC SOUND WAVE 4HE PHYSICAL QUALITIES OF SOUND ARE WAVE MUST HAVE A RANGE OF TO (Z WHICH IS THE AUDIBLE RANGE OF SOUND FOR HUMANS s !UDIBLE RANGE OF SOUND 7HILE MANY VEHICLE NOISES ARE CAPABLE OF BEING s 0ITCH HEARD SOME .6( NOISES ARE NOT IN THE AUDIBLE RANGE s )NTENSITY ,OW SPEED DRONING IS AN EXAMPLE OF A LOW FREQUENCY .6( CONCERN THAT MAY HAVE !LL PEOPLE HAVE DIFFERENT CAPABILITIES FOR HEARING COMPONENTS NOT IN THE AUDIBLE RANGE 4HIS SOUND 3OME PEOPLE MAY NOT HEAR SOUNDS CONDITION EXERTS PRESSURE ON THE DRIVERS THAT OTHER PEOPLE CAN HEAR +EEP THESE FACTS IN EARDRUM AND CAN BE EXTREMELY UNCOMFORTABLE MIND WHILE DIAGNOSING NOISE CONCERNS -OST /N THE OTHER END OF THE AUDIBLE RANGE OF VEHICLE CUSTOMERS BECOME TUNED INTO A NOISE AFTER NOISES ARE WIND NOISE AND BRAKE SQUEAKING HEARING IT REPETITIVELY 4HE HIGH FREQUENCIES OF THESE .6( CONCERNS PRODUCE A HIGH PITCHED NOISE THAT CAN BE 7HEN DIAGNOSING A VEHICLE IT MAY EXTREMELY ANNOYING 4HE lGURE BELOW ILLUSTRATES BE BENElCIAL TO HAVE THE CUSTOMER THE AUDIBLE RANGE OF AUTOMOTIVE NOISES REPRODUCE THE NOISE DURING A ROAD TEST
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-AXIMUM !UDIBLE ,EVEL
!VERAGE !UDIBLE ,EVEL -INIMUM !UDIBLE ,EVEL
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4HEORY .6( 4ERMINOLOGY 4HERE ARE COMMON TERMS USED WHEN DISCUSSING AN .6( CONCERN 4HE FOLLOWING TERMS AND GRAPHICS WILL HELP WHEN DISCUSSING .6( WITH OTHER PEOPLE WITH A TECHNICAL BACKGROUND
#YCLE #YCLE IS THE PATH A WAVE TRAVELS BEFORE THE WAVE BEGINS TO REPEAT THE PATH AGAIN )F AN !LTERNATING #URRENT !# SINE WAVE BEGINS A PATH AT ZERO VOLTS THE WAVE COMPLETES ONE CYCLE WHEN IT RETURNS TO ZERO VOLTS FROM A POSITIVE VOLTAGE
)N OTHER WORDS THE WAVE COMPLETES ONE CYCLE BY TRAVELING THE PATH FROM A NEGATIVE VOLTAGE TO ZERO VOLTS THEN TO A POSITIVE VOLTAGE AND THEN BACK TO ZERO VOLTS
&REQUENCY &REQUENCY IS THE NUMBER OF COMPLETE CYCLES THAT OCCUR IN ONE SECOND 3OUND AND VIBRATION WAVES ARE MEASURED IN (Z OR #YCLES 0ER 3ECOND #03 /NE (Z IS EQUAL TO ONE #03
4HE SOUND WAVE IN THE lGURE BELOW HAS A FREQUENCY OF (Z BECAUSE IT COMPLETES SEVEN #03 4HE FREQUENCY OF A SOUND OR VIBRATION CAN AID IN TROUBLESHOOTING AN .6( CONCERN
" " " " " " " !" ! " #
4HEORY 0ITCH 0ITCH IS THE PHYSICAL QUALITY OF SOUND THAT RELATES TO THE FREQUENCY OF THE WAVE )NCREASING THE FREQUENCY OF A SOUND INCREASES THE PITCH OF THE SOUND )F FREQUENCY DECREASES PITCH ALSO DECREASES
-AXIMUM
,ISTENING TO AN ACCESSORY DRIVE BELT SQUEAKING IS AN EXAMPLE OF A HIGH PITCHED HIGH FREQUENCY TYPE OF NOISE ! HIGH PITCHED HIGH FREQUENCY NOISE IS IRRITATING TO MOST PEOPLE
!MPLITUDE 0ITCH
! ROLLER BEARING THAT MAKES NOISE IS AN EXAMPLE OF A LOW PITCHED LOW FREQUENCY TYPE OF NOISE
-INIMUM
!MPLITUDE REFERS TO THE VERTICAL MEASUREMENT BETWEEN THE TOP AND THE BOTTOM OF A WAVE 4WO WAVES CAN HAVE THE SAME FREQUENCY BUT DIFFER IN AMPLITUDE !MPLITUDE IS THE QUANTITY OR AMOUNT OF ENERGY PRODUCED BY A VIBRATING COMPONENT
!-0,)45
%$!MPLITUDE
(IGH &REQUENCY (IGH 0ITCH
,OW &REQUENCY ,OW 0ITCH 4)-%
4HEORY 3OUND )NTENSITY 3OUND INTENSITY IS THE PHYSICAL QUALITY OF SOUND THAT RELATES TO THE AMOUNT AND DIRECTION OF THE mOW OF ACOUSTIC ENERGY AT A GIVEN POSITION 4HE lGURE ILLUSTRATES TWO SOUND WAVES WITH THE SAME FREQUENCY BUT DIFFERENT AMPLITUDES DIFFERENT INTENSITY LEVELS 3OUND INTENSITY IS MEASURED IN DECIBELS ! DECIBEL IS A UNIT FOR EXPRESSING RELATIVE DIFFERENCE IN POWER BETWEEN ACOUSTIC SIGNALS 3OUNDS GREATER THAN DECIBELS ARE DANGEROUS TO HUMAN HEARING
!-0,)45
%$$IFFERENCES IN PITCH THE SOURCE OF EACH SOUND OR THE PERSON WHO HEARS THE SOUND CAN CREATE THE PERCEPTION THAT TWO SOUNDS OF THE SAME INTENSITY HAVE DIFFERENT LEVELS OF LOUDNESS ,OW !MPLITUDE ,OW )NTENSITY
(IGH !MPLITUDE (IGH )NTENSITY 4)-%
4HEORY 2ESONANCE 2ESONANCE IS THE TENDENCY OF A SYSTEM TO RESPOND TO A COMPELLING FORCE OSCILLATING AT OR NEAR THE NATURAL FREQUENCY OF THE SYSTEM !LL OBJECTS HAVE NATURAL FREQUENCIES AND EXPERIENCE MAXIMUM RESPONSE AT THE POINT OF RESONANCE
4HE AMPLITUDE OF A VIBRATION IS GREATEST AT THE POINT OF RESONANCE !LTHOUGH THE VIBRATION CAN BE FELT ABOVE AND BELOW THE PROBLEM SPEED IT IS MOST PROMINENT AT THE POINT OF RESONANCE
2ESONANCE EXPLAINS WHY A TIRE VIBRATION OCCURS AT CERTAIN VEHICLE SPEEDS )F THE VEHICLEgS 4HE NATURAL FREQUENCY OF A TYPICAL AUTOMOTIVE SUSPENSION HAS A NATURAL FREQUENCY OF (Z FRONT SUSPENSION IS IN THE TO (Z RANGE 4HIS THE SUSPENSION WILL TRANSMIT OR RESONATE THE IS DESIGNED FOR RIDE AND HANDLING CONSIDERATIONS VIBRATION AT SPEEDS IN THE (Z RANGE 4HE !S SEEN IN THE lGURE THE SUSPENSIONS NATURAL VEHICLE WILL VIBRATE AT MPH MPH AND FREQUENCY IS THE SAME NO MATTER WHAT THE MPH BECAUSE THESE SPEEDS CAUSE A TIRE VEHICLE SPEED !S THE TIRE SPEED INCREASES VIBRATION TO RESONATE THROUGH THE SUSPENSION ALONG WITH THE VEHICLE SPEED THE DISTURBANCE INTO THE VEHICLE CREATED BY THE UNBALANCED TIRE INCREASES IN FREQUENCY %VENTUALLY THE FREQUENCY OF THE UNBALANCED TIRE INTERSECTS WITH THE NATURAL FREQUENCY OF THE SUSPENSION CAUSING THE SUSPENSION TO VIBRATE 4HIS INTERSECTION POINT IS CALLED THE RESONANCE
0OINT OF 2ESONANCE
(Z
3USPENSION &REQUENCY
RCE O & G
6IBRATION 3PEED
IN
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M
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4HEORY 4YPES OF .OISE 4HERE CAN BE MANY TYPES OF NOISE CONCERNS ON A VEHICLE 4HE CLASSIlCATION OF NOISES ASSISTS THE TECHNICIAN IN TROUBLESHOOTING AND REPAIRING THE CUSTOMERS VEHICLE
.OISE CAN BE ANNOYING TO SOME PEOPLE WHILE OTHERS lND IT ACCEPTABLE !UTOMOTIVE NOISES CAN BE AUDIBLE AT CERTAIN SPEEDS OR UNDER CERTAIN DRIVING CONDITIONS ! GEAR DRIVEN UNIT SUCH AS AN AUTOMOTIVE DRIVE AXLE PRODUCES A .OISE IS AN UNPLEASANT OR UNEXPECTED SOUND CREATED BY A VIBRATING OBJECT )NTERPRETATION PLAYS CERTAIN AMOUNT OF NOISE )N DEALING WITH THESE CONCERNS IT IS IMPORTANT TO KNOW WHAT A NORMAL A LARGE ROLE IN DElNING NOISE CHARACTERISTICS CONDITION IS AND EXPLAIN IT TO THE CUSTOMER IN 4ERMS USED TO DESCRIBE NOISE INCLUDE TERMS THEY CAN UNDERSTAND s $RONING 4RYING TO REPAIR A NORMAL VEHICLE CONDITION CAN BE FRUSTRATING $ESPITE GOOD INTENTIONS AN s "EAT ATTEMPTED REPAIR CAN ALSO BECOME A LIABILITY IF s 2OAD NOISE LEGAL ACTION IS INITIATED s "RAKE SQUEAL 4HE FREQUENCY OF NOISE VIBRATIONS IS MUCH HIGHER THAN THAT WHICH CAN ONLY BE FELT OFTEN RANGING BETWEEN AND (Z #ERTAIN NOISES CAN BE ASSOCIATED WITH THE COMPONENT SYSTEMS OF A VEHICLE SUCH AS THE ENGINE DRIVELINE AXLE BRAKES OR BODY COMPONENTS )N OTHER SITUATIONS A NOISE CAN TELEGRAPH THROUGH THE BODY OF A VEHICLE &OR EXAMPLE A CHIRPING NOISE MAY BE HEARD IN THE AREA OF THE INSTRUMENT PANEL WHEN IN FACT IT IS BEING PRODUCED BY THE REAR BRAKES 4HE SOUND HAS TRAVELED OR TELEGRAPHED THROUGH THE PARKING BRAKE CABLES &OLLOWING A SYSTEMATIC APPROACH WHEN TROUBLESHOOTING AN .6( CONCERN HELPS TO LOCATE THE CAUSE AND CORRECT THE CONDITION
4HEORY $RONING 4HE SENSATION PEOPLE EXPERIENCE WHEN DRIVING INTO A TUNNEL AT HIGH SPEED OR CLIMBING TO A HIGH ALTITUDE IS A FEELING OF EAR DISCOMFORT 4HE EAR DRUMS FEEL AS IF THEY ARE BEING FORCED IN OR OUT DUE TO SUDDEN CHANGES IN ATMOSPHERIC PRESSURE !N UNPLEASANT DRONING CAUSES A SIMILAR SENSATION DUE TO LARGE mUCTUATIONS OF AIR PRESSURE IN THE CAR ! CUSTOMER MAY REFER TO UNPLEASANT DRONING NOISES AS HUMMING NOISES 4HERE ARE THREE TYPES OF UNPLEASANT DRONING s ,OW SPEED s -IDDLE SPEED s (IGH SPEED
5NPLEASANT DRONING AT LOW AND MIDDLE SPEED DRIVING IS A LONG DURATION LOW PITCHED NOISE THAT IS NON DIRECTIONAL )T IS HARD TO HEAR AND FEELS LIKE PRESSURE IN THE EARS &EELING A SMALL AMPLITUDE VIBRATION IS COMMON WITH LOW AND MIDDLE SPEED DRONING ,OW SPEED DRONING HAS A RANGE OF UP TO MPH KPH AND HAS A FREQUENCY OF TO (Z -IDDLE SPEED DRONING HAS A RANGE OF TO MPH TO KPH WITH A FREQUENCY OF TO (Z 5NPLEASANT DRONING AT HIGH SPEED DRIVING IS A LONG DURATION NON DIRECTIONAL HUMMING NOISE THAT IS UNCOMFORTABLE TO THE EARS (IGH SPEED DRONING HAS A RANGE OF MPH KPH AND UP WITH A FREQUENCY OF TO (Z 4HE THREE CLASSIlCATIONS OF DRONING ARE SPEED AND FREQUENCY RELATED ! LOW SPEED DRONING SOUND HAS A LOWER PITCH THAN A HIGH SPEED DRONING SOUND 4HE TABLE SUMMARIZES THE SPEED AND FREQUENCY RANGES FOR THE THREE TYPES OF DRONING
3PEED AND &REQUENCY 2ANGES OF $RONING 30%%$ 2!.'%
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,OW 3PEED $RONING
5P TO MPH KPH
TO (Z
-IDDLE 3PEED $RONING
TO MPH TO KPH
TO (Z
(IGH 3PEED $RONING
MPH TO (Z KPH AND UP
4HEORY $RONING CAN OCCUR WHEN ACCELERATING DECELERATING OR DRIVING AT A CONSTANT SPEED BUT MOST OFTEN OCCURS WHEN ACCELERATING $RONING USUALLY IS APPARENT AT A SPECIlC ENGINE RPM OR VEHICLE SPEED &OR EXAMPLE THE lGURE ILLUSTRATES HOW THE NOISE LEVEL OF A VEHICLE INCREASES WITH VEHICLE SPEED !S VEHICLE SPEED REACHES A CERTAIN RANGE THE SOLID COLORED AREAS OF THE lGURE A LARGE INCREASE IN THE NOISE LEVEL OCCURS
4HE SPEED OR RPM RANGE AT WHICH UNPLEASANT DRONING OCCURS IS RELATIVELY NARROW 7HEN DRONING OCCURS AT A SPECIlC VEHICLE SPEED THE RANGE IS GENERALLY WITHIN MPH KPH OF THAT SPEED 7HEN DRONING OCCURS AT A SPECIlC ENGINE RPM THE TECHNICIAN SHOULD CHANGE VEHICLE SPEED VERY SLOWLY #HANGING VEHICLE SPEED QUICKLY WILL MAKE IT DIFlCULT TO CHECK THE DRONING BECAUSE RPM WILL PASS THROUGH THE SPECIlC RANGE TOO QUICKLY $RONING IS USUALLY GENERATED BY MORE THAN ONE COMPONENT )N MOST CASES IT IS NECESSARY TO ELIMINATE ALL THE CAUSES IN ORDER TO REMOVE THE DRONING NOISE &OR EXAMPLE UNPLEASANT DRONING CAN OCCUR WHEN ENGINE AND DRIVELINE VIBRATIONS ARE TRANSMITTED TO THE BODY PANELS CAUSING THEM TO RESONATE !IR CLEANER AIR INTAKE AND EXHAUST NOISES CAN COMBINE AND CAUSE DRONING IN THE PASSENGER COMPARTMENT /THER ITEMS THAT ARE SOMETIMES RESPONSIBLE FOR UNPLEASANT DRONING INCLUDE s "ENDING RESONANCE OF EXHAUST PIPES
s 2ESONANCE OF AUXILIARY EQUIPMENT s "ENDING RESONANCE OF PROPELLER SHAFT s 2ESONANCE OF SUSPENSION LINKS
s 4RANSMISSION OF ENGINE VIBRATION
s 4RANSMISSION OF EXHAUST NOISE s 4RANSMISSION OF INTAKE AIR NOISE
4HE BENDING RESONANCE IS A NORMAL OCCURRENCE FOR STRAIGHT TUBES AND PIPES AND EXHAUST AND DRIVE SHAFTS 4HESE COMPONENTS DEFORM RESONATE AT KNOWN FREQUENCIES %NGINEERS DESIGN COMPONENTS SO THAT THE BENDING RESONANCE WILL NOT OCCUR DURING THE NORMAL OPERATION OF THE VEHICLE
4HEORY "EAT &OR BEAT SOUNDS TO DEVELOP THERE MUST BE TWO SOUND SOURCES &OR EXAMPLE STRIKING A TUNING FORK PRODUCES A PURE TONE OF A CERTAIN FREQUENCY PITCH )F A SECOND TUNING FORK WITH A VERY DIFFERENT PITCH IS STRUCK EACH TONE IS DISTINGUISHABLE FROM ONE ANOTHER (OWEVER IF THE PITCHES OF THE TUNING FORKS ARE SIMILAR THE TWO TONES PRODUCE A BEAT SOUND WITH A PITCH THAT OCCURS IN CYCLES AT THE DIFFERENCE OF THE TWO FREQUENCIES )F THE PITCHES OF THE TWO SOUNDS ARE THE SAME OR ONLY SLIGHTLY DIFFERENT THEY ARE INDISTINGUISHABLE AND ARE PERCEIVED AS ONE SOUND 4HE lGURE ILLUSTRATES TWO TUNING FORKS PRODUCING SOUND WAVES WITH TROUGHS AND PEAKS 4HE TWO WAVES HAVE SLIGHTLY DIFFERENT FREQUENCIES 4HE SOUND LEVEL BECOMES HIGHER WHEN THEIR PEAKS OCCUR AT THE SAME TIME 4HE SOUND LEVEL DROPS WHEN A PEAK OF ONE WAVE OCCURS AT THE SAME TIME AS THE TROUGH OF THE OTHER WAVE 7HEN THE TWO WAVES COMBINE THEY PRODUCE A BEAT SOUND IN WHICH LOUDNESS CHANGES PERIODICALLY
4HE SENSATION OF A BEAT SOUND IS MOST NOTICEABLE WHEN THE FREQUENCY DIFFERENCE IS TO (Z )F THE TWO FREQUENCIES ARE CLOSER THEIR TONES ARE INDISTINGUISHABLE AND ARE SENSED AS THE SAME SOUND )F THE TWO FREQUENCIES ARE GREATER THAN (Z APART EACH TONE IS DISTINGUISHABLE FROM ONE ANOTHER "EAT SOUNDS CAN RESULT FROM A COMBINATION OF MANY TYPES OF VIBRATIONS #OMMON COMBINATIONS THAT RESULT IN BEAT SOUNDS INCLUDE s %NGINE AND AIR CONDITIONING COMPRESSOR s %NGINE AND POWER STEERING HYDRAULIC PUMP OR OTHER ACCESSORIES s %NGINE AND VIBRATIONS OF THE DRIVE SHAFT s 4IRE NON UNIFORMITY s 4IRE AND DRIVE SHAFT VIBRATIONS
! (Z
" (Z
#
3OUND 7AVES # ARE THE SUM OF 3OUND 7AVES ! AND " 4HE mUCTUATION IN -AGNITUDE IS 0HASING OR "EATING
4HEORY 2OAD .OISE 4HE SOUNDS THAT OCCUR WHILE DRIVING ON GRAVEL OR ROUGHLY PAVED ROADS IS AN EXAMPLE OF ROAD NOISE 4HIS TYPE OF NOISE IS CONTINUOUS AND HAS A CONSTANT CHARACTER 2OAD NOISE CAN OCCUR AT ALL VEHICLE SPEEDS OR WHEN THE VEHICLE IS COASTING AND HAS A FREQUENCY RANGE OF TO (Z ! VERY lNE VIBRATION ALSO MAY BE NOTICEABLE 2OAD ROUGHNESS AND TIRES ARE MAJOR SOURCES OF NOISE AND VIBRATION THAT OCCUR DURING DRIVING 3INCE THE SOURCE OF ROAD NOISE IS IRREGULAR ROAD SURFACES DIFFERENT TYPES OF TIRES CAN INmUENCE THE AMOUNT OF ROAD NOISE 4HE IMPACT FORCE FROM ROAD SURFACES TRANSMITS TO THE TIRES CAUSING THEM TO VIBRATE 4HIS VIBRATION IN TURN TRANSMITS TO THE SUSPENSION AND BODY 4HE RESONANCE CHARACTERISTIC OF THE PASSENGER COMPARTMENT AMPLIlES THE VIBRATION AND GENERATES ANNOYING ROAD NOISE
4HEORY "RAKE 3QUEAL 4HE MOST COMMON BRAKE SYSTEM .6( CONCERN IS BRAKE SQUEAL "RAKE SQUEAL IS A HIGH PITCHED NOISE )F BRAKE SQUEAL ONLY APPEARS WHEN THE VEHICLE IS lRST PUT INTO OPERATION IT MAY BE DUE TO MOISTURE ON THE BRAKE LININGS "RAKE SQUEAL ALSO CAN OCCUR WHEN FRICTION IS CREATED BETWEEN BRAKE COMPONENTS DURING BRAKING 7ORN OR DAMAGED BRAKE COMPONENTS CAN PRODUCE A VIBRATION RESULTING IN BRAKE SQUEAL 4HIS HIGH FREQUENCY NOISE CAN OCCUR UNDER DIFFERENT BRAKE PEDAL PRESSURES VEHICLE SPEEDS AND BRAKE TEMPERATURES $RUM BRAKES USUALLY EMIT A LOWER PITCH NOISE THAT GETS LOUDER WITH INCREASED BRAKE PEDAL PRESSURE $ISC BRAKE NOISE IS GENERALLY A HIGH PITCHED SQUEAL THAT OCCURS UNDER LIGHT PEDAL PRESSURE 4HE MAJOR VIBRATION SOURCES OF BRAKE SQUEAL ARE s 7ORN BRAKE SHOES s .ON UNIFORM THICKNESS OF BRAKE DISC OR DRUMS s %XCESSIVE RUNOUT s $AMAGE OR CONTAMINATION OF FRICTION SURFACES "ECAUSE OF THE COMPLEX NATURE OF BRAKES AND THE MANY DIFFERENT PARTS FOUND IN THEM THE BEST WAY TO CORRECT BRAKE SQUEAL IS TO FOLLOW SERVICE PROCEDURES $URING BRAKE SERVICE ALWAYS THOROUGHLY CLEAN ANY FRICTION SURFACE BEFORE REASSEMBLING THE BRAKE ! WIDE VARIETY OF COATING MATERIALS USED ON BRAKE BACKING SURFACES AND THE INSTALLATION OF SHIMS AND CLIPS CAN HELP ELIMINATE BRAKE SQUEAL .6( CONCERNS
4HEORY #OMPELLING &ORCE AND 6IBRATING "ODY 6IBRATIONS OCCUR WHEN THERE IS A COMPELLING FORCE OR EXCITING FORCE ACTING UPON AN OBJECT THAT CAUSES THE BODY TO VIBRATE ,OCATING THE COMPELLING FORCE THE SOURCE OF THE VIBRATION CAN ASSIST IN ELIMINATING AN .6( CONCERN 4HE MAJOR COMPONENT GROUPS THAT PRODUCE COMPELLING FORCES ARE s 4IRE AND WHEEL s $RIVELINE s %NGINE AND TORQUE CONVERTER
6IBRATION 6IBRATION IS THE REPETITIVE MOTION OF AN OBJECT BACK AND FORTH OR UP AND DOWN 4HIS MOTION IS A FUNCTION OF TIME AND IS MEASURABLE IN (Z 6IBRATION CAN BE DESCRIBED IN MANY WAYS WHICH INCLUDE s 3HAKE s 3HIMMY s 3HUDDER 6IBRATIONS CAN BE CONSTANT OR VARIABLE AND OCCUR DURING A PORTION OF THE TOTAL OPERATING SPEED RANGE 6IBRATIONS USUALLY ARE CAUSED BY SOME ROTATING COMPONENT OR COMPONENTS OR SOMETIMES BY THE COMBUSTION OF THE AIRFUEL MIXTURE IN THE INDIVIDUAL ENGINE CYLINDERS
5NDER NORMAL CIRCUMSTANCES A ROTATING COMPONENT DOES NOT PRODUCE A NOTICEABLE VIBRATION (OWEVER IF THE COMPONENT HAS IMPROPER WEIGHT DISTRIBUTION IMBALANCE OR IS ROTATING IN AN ECCENTRIC PATTERN OUT OF ROUND OR BENT THEN A NOTICEABLE VIBRATION MAY BE PRODUCED )F THE CHARACTERISTICS OF THE VIBRATION CAN BE MEASURED THE INFORMATION ABOUT THE VIBRATION CAN BE USED TO MATCH IT WITH COMPONENTS THAT ARE THE LIKELY CAUSE 4HERE ARE MANY TYPES OF VIBRATION PROBLEMS ON A VEHICLE 4HE CLASSIlCATION OF VIBRATIONS ASSISTS THE TECHNICIAN IN TROUBLESHOOTING AND REPAIRING THE CUSTOMER CONCERN
6IBRATION 4RANSFER 0ATH 6IBRATIONS TRAVEL THROUGH A VEHICLES STRUCTURE SIMILAR TO THE WAY RADIO WAVES TRAVEL THROUGH AIR 6IBRATIONS ARE OFTEN NOTICED IN A COMPONENT FAR REMOVED FROM WHERE THEY ARE GENERATED 4RANSMISSION OF A VIBRATION TO OTHER COMPONENTS IS CALLED hTELEGRAPHINGv &OR EXAMPLE AN OUT OF BALANCE FRONT TIRE AND WHEEL ASSEMBLY MAY RESULT IN A NOTICEABLE STEERING WHEEL SHAKE )N THIS CASE THE WHEEL AND TIRE ASSEMBLY IS THE ORIGINATOR OF THE VIBRATION THE SUSPENSION IS THE CONDUCTOR AND THE STEERING WHEEL IS THE REACTOR
4HEORY 6IBRATION /RDER /RDER IS THE NUMBER OF DISTURBANCES CREATED IN ONE REVOLUTION OF A COMPONENT ! SINGLE HIGH SPOT ON A TIRE CAUSES ONE DISTURBANCE PER REVOLUTION AND IS CALLED A lRST ORDER DISTURBANCE )F THE WHEEL ROTATES TIMES PER SECOND THERE ARE DISTURBANCES PER SECOND 4HIS CREATES A lRST ORDER DISTURBANCE OF (Z )F THE TIRE DEVELOPED A SECOND HIGH SPOT A SECOND ORDER DISTURBANCE WOULD RESULT 4HE WHEEL ROTATING TIMES PER SECOND PRODUCES DISTURBANCES PER SECOND 4HIS CREATES A SECOND ORDER DISTURBANCE OF (Z 4HREE HIGH SPOTS CREATE A THIRD ORDER DISTURBANCE AND FOUR HIGH SPOTS CREATE A FOURTH ORDER DISTURBANCE (IGHER ORDER DISTURBANCES CONTINUE TO PROGRESS IN THIS WAY
4HE VIBRATION ORDER CAN AID THE TECHNICIAN WHILE TROUBLESHOOTING &OR EXAMPLE A VEHICLE HAS AN .6( CONCERN THAT IS PRODUCING A VIBRATION AT (Z !FTER CALCULATING DRIVE SHAFT FREQUENCY IT IS DETERMINED THE DRIVE SHAFT HAS A FREQUENCY OF (Z 4HE SECOND ORDER FREQUENCY OF THE DRIVE SHAFT IS (Z 4HIS MATCHES THE FREQUENCY OF THE .6( CONCERN "Y DETERMINING THAT THE .6( CONCERN IS A POSSIBLE SECOND ORDER VIBRATION YOU WOULD LOOK AT COMPONENTS THAT COULD CAUSE A VIBRATION OF THIS TYPE 5NIVERSAL JOINTS WOULD BE A GOOD COMPONENT TO CHECK BECAUSE IT IS POSSIBLE THEY COULD PRODUCE TWO DISTURBANCES WITH EACH REVOLUTION OF THE DRIVE SHAFT ! MISSING DRIVE SHAFT WEIGHT COULD BE ELIMINATED FROM THE LIST OF POSSIBILITIES BECAUSE THIS SITUATION WOULD PRODUCE A VIBRATION OF THE lRST ORDER
&IRST ORDER 6IBRATION
3ECOND ORDER 6IBRATION
4HEORY 6IBRATION /RDER %XAMPLES (ALF ORDER VIBRATION
3ECOND ORDER VIBRATION
(ALF ORDER VIBRATION IS CREATED WHEN ANY COMPONENT THAT ROTATES AT HALF THE CRANKSHAFT SPEED IS OUT OF BALANCE OR HAS EXCESSIVE RUNOUT !N EXAMPLE OF THIS IS CAMSHAFT IMBALANCE "ALANCING THE COMPONENT OR CORRECTING THE RUNOUT MAY BRING THE VIBRATION TO AN ACCEPTABLE LEVEL
3ECOND ORDER VIBRATION IS CAUSED BY THE UP AND DOWN MOTION OF THE PISTONS 4HIS REVERSAL OF MASS AND MOTION CREATES A NATURAL VIBRATION
&IRST ORDER VIBRATION &IRST ORDER VIBRATION IS CREATED WHEN ANY COMPONENT THAT ROTATES AT CRANKSHAFT SPEED IS OUT OF BALANCE OR HAS EXCESSIVE RUNOUT %XAMPLES ARE mYWHEEL OR TORQUE CONVERTER IMBALANCE AND CYLINDER TO CYLINDER MASS DIFFERENCES )N RARE CASES THE CRANKSHAFT ITSELF MAY BE IMBALANCED "ALANCING THE COMPONENT OR CORRECTING THE RUNOUT MAY BRING THE VIBRATION TO AN ACCEPTABLE LEVEL
3YMPTOMS OF ENGINE IMBALANCE INCLUDE s ! LOW SPEED SHAKE FELT BETWEEN AND 2EVOLUTIONS 0ER -INUTE RPM THAT HAS A FREQUENCY OF TO (Z s ! ROUGHNESS SOMETIMES FELT AND HEARD BETWEEN TO RPM AT A FREQUENCY OF TO (Z &IRST AND SECOND ORDER ENGINE VIBRATIONS USUALLY ARE DETECTED DURING THE NEUTRAL RUN UP TEST
4HIRD ORDER VIBRATION ! THIRD ORDER VIBRATION IS CAUSED BY ANY COMPONENT THAT HAS THREE HEAVY SPOTS
4HEORY 4YPES OF 6IBRATION 6IBRATIONS IN A VEHICLE CAN BE ANY ONE OF THE FOLLOWING TYPES s 3HAKE s 3HIMMY s "RAKE 6IBRATION3HUDDER
3HAKE 6IBRATIONS AT THE STEERING WHEEL OR SEAT OR AN ANNOYING VIBRATION AT THE mOOR ARE INDICATORS OF hSHAKEv 3HAKE GENERALLY HAS A FREQUENCY OF TO (Z 4HERE ARE TWO TYPES OF SHAKE s 6ERTICAL UP AND DOWN s ,ATERAL SIDE TO SIDE 6ERTICAL SHAKE IS SEVERE VERTICAL VIBRATION OF THE BODY SEATS AND STEERING WHEEL ! TREMBLING ENGINE HOOD OR REARVIEW MIRROR ALSO CAN BE A VERTICAL SHAKE SYMPTOM ,ATERAL SHAKE IS SIDE TO SIDE VIBRATION OF THE BODY SEATS AND STEERING WHEEL ! TREMBLING VIBRATION IN THE DRIVERS WAIST OR HIPS MAY BE A SYMPTOM OF A LATERAL SHAKE 4HE MAJOR VIBRATION SOURCES OF VERTICAL AND LATERAL SHAKE ARE s 2OUGHNESS OF ROAD s 4IRE IMBALANCE s .ON UNIFORM TIRES s "ENT OR OUT OF ROUND WHEELS s $RIVELINE s %NGINE
4HEORY 3HIMMY 6IBRATION THAT CAUSES THE STEERING WHEEL TO OSCILLATE IS KNOWN AS hSHIMMYv 4HE BODY OF THE VEHICLE ALSO MAY VIBRATE LATERALLY 3HIMMY GENERALLY HAS A FREQUENCY OF TO (Z 4HERE ARE TWO TYPES OF SHIMMY s (IGH SPEED SHIMMY s ,OW SPEED SHIMMY (IGH SPEED SHIMMY OCCURS WHEN DRIVING ON SMOOTH ROADS AT HIGH SPEEDS (IGH SPEED SHIMMY TYPICALLY HAS A LIMITED SPEED RANGE IN WHICH SYMPTOMS ARE NOTICEABLE ,OW SPEED SHIMMY OCCURS WHEN THE STEERING WHEEL BEGINS TO VIBRATE AS THE VEHICLE IS DRIVEN ACROSS A BUMP AT LOW SPEEDS
4HE MAJOR VIBRATION SOURCES OF HIGH SPEED AND LOW SPEED SHIMMY ARE s 2OUGHNESS OF ROAD s 4IRE IMBALANCE s .ON UNIFORM TIRES s "ENT OR OUT OF ROUND WHEELS &OR EXAMPLE A TIRE WITH EXCESSIVE RUNOUT OUT OF BALANCE OR OUT OF ROUND MAY CAUSE HIGH OR LOW SPEED SHIMMY 4HIS IS BECAUSE THE TIRE FAULT GENERATES A VIBRATION AT A PARTICULAR FREQUENCY 7HEN THE VIBRATION OF THE TIRE REACHES THE NATURAL FREQUENCY OF THE VEHICLES FRONT UNSPRUNG COMPONENTS SUCH AS THE FRONT AXLE TIRES AND WHEELS THEY START TO VIBRATE 7HEN THE FREQUENCY OF THE FRONT UNSPRUNG COMPONENTS MATCHES THE NATURAL FREQUENCY OF THE STEERING SYSTEM RESONANCE OCCURS 4HIS RESONANCE CAUSES THE STEERING WHEEL TO VIBRATE HEAVILY IN THE TURNING DIRECTION
4HEORY "RAKE 6IBRATION3HUDDER "RAKE VIBRATIONSHUDDER IS TRANSMITTED THROUGH THE BRAKE HYDRAULIC LINES TO THE SUSPENSION SYSTEM STEERING SYSTEM AND THE BRAKE PEDAL "RAKE PEDAL PULSATION IS GENERATED WHEN APPLYING A BRAKE WITH A NON UNIFORM DIAMETER DRUM OR A DISC BRAKE WITH NON UNIFORM BRAKE DISC THICKNESS "RAKE SHUDDER CAUSES THE INSTRUMENT PANEL STEERING WHEEL AND SOMETIMES THE ENTIRE BODY TO VIBRATE VERTICALLY AND BACK AND FORTH DURING BRAKING )T ALSO MAY RESULT IN BRAKE PEDAL PULSATION RELATED TO WHEEL ROTATION AND CAN OCCUR DURING ANY BRAKING CONDITION OR VEHICLE SPEED .ORMALLY BRAKE SHUDDER HAS A PEAK AT TO MPH TO KPH AND HAS A FREQUENCY OF TO (Z #ERTAIN OPERATING CONDITIONS CAN AFFECT THE CAUSE OF THESE VIBRATIONS 4HESE INCLUDE s %XTENDED PERIODS WHERE THE VEHICLE IS NOT IN OPERATION s "RAKE DISC SURFACE IRREGULARITIES DUE TO FOREIGN AGENTS OIL OR GREASE ANTIFREEZE ETC s $EFORMATION OF BRAKE DRUM DUE TO POOR INSTALLATION
)F THE DISC ROTOR HAS EXCESSIVE THICKNESS VARIATION FRICTION FORCE ON THE BRAKING SURFACE VARIES DURING BRAKE APPLICATION 4HE CHANGE IN THE BRAKING FORCE GENERATES A VIBRATION AT A CERTAIN FREQUENCY 4HIS VIBRATION IS TRANSMITTED TO THE SUSPENSION STEERING AND BRAKE PEDAL 4HE VIBRATION CAN ALSO TRANSMIT TO THE BODY CAUSING IT TO RESONATE 4HE ROOT CAUSE OF DISC BRAKE VIBRATIONSHUDDER CONCERNS IS THICKNESS VARIATION 4HICKNESS VARIATION CAN BE CAUSED BY A ROTOR THAT HAS LATERAL RUNOUT ,ATERAL RUNOUT CAN BE CAUSED BY IMPROPER WHEEL TIGHTENING PROCEDURES AND TORQUE VALUES AS WELL AS HUB RUNOUT !S THE ROTOR WOBBLES LATERAL RUNOUT CONTACT IS MADE WITH THE BRAKE PADS !S SECTIONS OF THE ROTOR MAKE CONTACT WITH THE PADS SMALL AMOUNTS OF METAL WEAR FROM THE ROTOR SURFACE 4HIS CONTINUES UNTIL ENOUGH METAL IS WORN IN SECTIONS TO CAUSE THICKNESS VARIATION 4HIS IS WHY IMPROPER WHEEL TIGHTENING PROCEDURES OFTEN TAKE WEEKS OR MONTHS TO PRODUCE BRAKE VIBRATIONS 4HE SAME IS TRUE FOR HUB RUNOUT 2ESURFACING OR REPLACING ROTORS WHEN THE HUB HAS LATERAL RUNOUT IS USUALLY A SHORT TERM REPAIR !LWAYS FOLLOW SERVICE INFORMATION FOR PROPER WHEEL TIGHTENING PROCEDURES AND TORQUE VALUES #HECK THE HUB FOR LATERAL RUNOUT WHEN RESURFACING OR REPLACING ROTORS FOR A BRAKE VIBRATION )F THE VIBRATION OR NOISE IS CAUSED BY THE BRAKE SYSTEM REFER TO SERVICE MANUAL INFORMATION FOR THE VEHICLE 0ROCEDURES TO CHECK DRUMS AND ROTORS FOR OUT OF ROUND THICKNESS VARIATION AND LATERAL RUNOUT ARE COVERED IN THE SERVICE INFORMATION /VERTIGHTENING WHEEL BOLTS SUCH AS WITH AN IMPACT WRENCH OFTEN CAUSES ROTOR WARPAGE "E SURE WHEEL NUTS ARE CORRECTLY TORQUED
4HEORY 2IDE #OMFORT 2IDE COMFORT PLAYS A LARGE PART IN A CUSTOMERS SATISFACTION WITH THEIR VEHICLE !VOIDING ABNORMAL VIBRATIONS ENSURES A QUALITY RIDE COMFORT LEVEL .ORMAL VEHICLE VIBRATIONS ARE A RESULT OF ROAD ROUGHNESS $URING NORMAL OPERATION THE VEHICLE EXPERIENCES VIBRATION BETWEEN THE SPRUNG COMPONENTS BODY AND SUSPENSION AND THE UNSPRUNG COMPONENTS AXLES TIRES AND WHEELS 4HIS IS AN ACCEPTABLE CONDITION UNLESS THE SPRUNG OR UNSPRUNG COMPONENTS BECOME DEFECTIVE WORN OR DAMAGED 7HEN UNSPRUNG COMPONENTS RESONATE WITH THE SPRUNG COMPONENTS THE RESULT IS POOR RIDE COMFORT 2IDE COMFORT VIBRATIONS MAY CAUSE THE VEHICLE TO ROLL PITCH AND BOUNCE WHICH MAY CAUSE A CUSTOMER CONCERN 0OOR RIDE COMFORT CAN BE MINIMIZED BY ENSURING SUSPENSION AND STEERING COMPONENTS ARE NOT DAMAGED OR WORN
4HEORY (ARSHNESS (ARSHNESS RESULTS WHEN THE VEHICLE IS UNABLE TO ABSORB VIBRATIONS PRODUCED BY ROAD CONDITIONS 4HE CAUSES MAY BE DUE TO DETERIORATION OF VEHICLE COMPONENTS DAMAGE OR MODIlCATION OF THE ORIGINAL EQUIPMENT )N MOST CASES HARSHNESS IS RELATED TO CHASSIS COMPONENTS 7HEN DIAGNOSING A HARSHNESS CONCERN PAY CLOSE ATTENTION TO INTERIOR NOISE LEVELS IN THE VEHICLE -ANY HARSHNESS CONDITIONS ARE DUE TO A COMPONENT THAT IS NOT ALLOWED TO MOVE WITHIN ITS NORMAL TRAVEL OR ONE THAT HAS LOST ITS ISOLATING GROMMETS OR BUSHINGS 4HIS MAKES ENGINE MOUNTS SUBFRAME MOUNTS BUSHINGS AND SUSPENSION COMPONENTS PRIME SUSPECTS IN THE DIAGNOSTIC PROCEDURE
-ANY CUSTOMERS USE THE WORD hHARSHNESSv TO DESCRIBE RIDE COMFORT CONCERNS (ARSHNESS HAS BECOME A UNIVERSAL TERM WHEN DEALING WITH .6( CONCERNS ON A VEHICLE &OR THE PURPOSE OF THIS COURSE HARSHNESS IS AN AGGRESSIVE SUSPENSION FEEL OR LACK OF hGIVEv IN RESPONSE TO A SINGLE INPUT )T CAN BE ASSOCIATED WITH AN ABRUPT THUMPING NOISE AS WELL AS AN AGGRESSIVE FEEL
/VERSIZED TIRES HEAVY DUTY SPRINGS AND SHOCKS OR OTHER VEHICLE MODIlCATIONS ALSO MUST BE CONSIDERED 3OME AFTERMARKET TIRES EVEN WHEN THEY ARE THE CORRECT SIZE MAY PRODUCE CHANGES IN THE VEHICLE THAT WILL GENERATE OWNER CONCERNS
(ARSHNESS OCCURS WHEN A VEHICLE VIBRATES FROM MOVING ACROSS ROAD JOINTS PROJECTIONS STEPPED DIFFERENCES OR DEPRESSIONS ON PAVED ROADS $RIVING ON THE EXPRESSWAY INCREASES THE PITCH OF THE THUMPING SOUND 4HE IMPACT FORCE FROM THE ROAD SURFACE CAUSES THE TIRES TO VIBRATE 4HE TIRES TRANSMIT THE VIBRATION THROUGH THE SUSPENSION SYSTEM TO THE CAR BODY (ARSHNESS HAS A FREQUENCY OF TO (Z
4HEORY 6IBRATIONS 6IBRATIONS ARE NOTICEABLE AT THE STEERING WHEEL SEATS AND mOOR 4HE LEVEL AND INTENSITY OF THE VIBRATION CHANGES WITH THE SUSPENSION TYPE AND THE BUSHINGS USED ,ONGITUDINAL IMPACT FORCES ARE TRANSMITTED TO THE LOWER ARMS WHERE SUSPENSION BUSHINGS DAMPEN THE VIBRATION 4HE DAMPENED VIBRATION THEN TRANSMITS THROUGH THE SUSPENSION CROSSMEMBER AND STRUT INSULATORS TO THE BODY 4HE RIGIDITY OF THE BUSHINGS AND INSULATORS IN THE VIBRATION TRANSMISSION PATH HAS A LARGE INmUENCE ON HARSHNESS 4HE USE OF LOW RIGIDITY BUSHINGS AND INSULATORS TO PROVIDE GREATER FORE AFT SUSPENSION COMPLIANCE SOFTENS THE IMPACT FORCE EFFECTIVELY BUT RESULTS IN LESS RESPONSIVE STEERING !LONG WITH SUSPENSION SYSTEM DESIGNS TIRE CHARACTERISTICS INmUENCE THE AMOUNT OF HARSHNESS 7HEN TIRES EXPERIENCE AN IMPACT FORCE FROM A PAVEMENT JOINT THEY DEFORM TO CUSHION THE REST OF THE VEHICLE 4HE TIRES ABSORB THE FORCE TO SOME EXTENT AND ARE AN IMPORTANT FACTOR WHEN DEALING WITH HARSHNESS !T THE SAME TIME THE DEFORMATION TRANSMITS VIBRATION TO OTHER PORTIONS OF THE TIRES 4HIS CAUSES THE TIRES TO UNDERGO COMPLICATED RESILIENT VIBRATIONS ! TIRE THAT CAN ABSORB VIBRATIONS FROM IMPACT IS EFlCIENT IN CONTROLLING THE PROBLEM OF HARSHNESS
)T IS EXTREMELY DIFlCULT FOR A TIRE TO ABSORB HARSHNESS VIBRATIONS COMPLETELY 4HESE VIBRATIONS INVOLVE NOT ONLY TIRE TYPE BUT ALSO INmATION PRESSURE 4HE TECHNICIAN SHOULD ALWAYS ENSURE PROPER TIRE INmATION PRESSURE WHEN TROUBLESHOOTING A HARSHNESS CONCERN 'ENERALLY A SOFT TIRE WITH ENVELOPING CHARACTERISTICS PERFORMS WELL IN PREVENTING HARSHNESS 2ADIAL TIRES HAVE RIGID TREADS AND ARE LOW IN ENVELOPING CHARACTERISTICS 4HEY TEND TO CAUSE HARSHNESS PARTICULARLY AT TO MPH TO KPH
$IAGNOSIS 'ETTING 'OOD )NFORMATION FROM 3ERVICE !DVISORS 4O PROPERLY DIAGNOSE AND REPAIR AN .6( CONCERN THE CONCERN WILL NEED TO BE DUPLICATED DURING A ROAD TEST 4HE SERVICE ADVISORS ARE A GOOD SOURCE FOR THE SYMPTOMS AND FACTS SURROUNDING THE CONCERN 0ROPER QUESTIONING OF THE CUSTOMER WILL USUALLY PROVIDE THE INFORMATION NECESSARY TO DUPLICATE THE CONCERN )F THE CUSTOMER IS LEAVING THE VEHICLE AND WILL BE UNAVAILABLE FOR A ROAD TEST LATER IN THE DAY THEN IT IS ADVISABLE THAT THE SERVICE ADVISOR OR TECHNICIAN ROAD TEST WITH THE CUSTOMER BEFOREHAND TO EXPERIENCE THE SYMPTOMS AND FACTS OF THE .6( CONCERN 4HE &OUR 3TEPS &OCUS THE DISCUSSION WITH THE CUSTOMER ON THE SYMPTOM DESCRIPTION
$IAGNOSING AND 3OLVING #USTOMER #ONCERNS $ESCRIBE THE CONCERN s ,IST KNOWN SYMPTOMS s !VOID OPINIONS OR DISGUISED SOLUTIONS 6ERIFY AND ANALYZE s 4RY TO DUPLICATE THE CONCERN s ,IST POSSIBLE CAUSES ,OCATE THE CONCERN s 3ELECT THE PROBABLE CAUSES s 0RIORITIZE TASKS s )DENTIFY THE CONCERN 2EPAIR THE CONCERN s $ETERMINE THE SPECIlC CAUSE
!SK QUESTIONS THAT CLARIFY WHAT WHEN WHERE AND HOW OFTEN 3UMMARIZE YOUR UNDERSTANDING AND GET AGREEMENT FROM THE CUSTOMER 5SE OPEN ENDED QUESTIONS TO PROMPT FOR SPECIlCS %XPLAIN WHAT YOU WILL DO TO PROCEED AND GET ACKNOWLEDGEMENT FROM THE CUSTOMER
s 0ERFORM THE REPAIR #ONDUCT A QUALITY CHECK s 2ECHECK FOR PROPER OPERATION AND REASSEMBLY s #HECK FOR CLEANLINESS AND APPEARANCE /THER )NFORMATION 3OURCES s !UDI %LECTRONIC 3ERVICE )NFORMATION 3YSTEM !%3)3 n 4ECHNICAL "ULLETINS s /THER TECHNICIANS s (ELPLINE s +NOWN GOOD VEHICLE s 4HIS TRAINING MANUAL s 4HE '30 6IBRATION #ONTROL 3YSTEM /PERATION )NSTRUCTIONS
$IAGNOSIS 0RE 2OAD 4EST )NSPECTION
2OAD 4EST 4IPS
"EGIN CHECKING THE VEHICLE WITH A VISUAL INSPECTION "E SURE TO CAREFULLY INSPECT THE TIRES UNLESS THE .6( CONCERN ONLY OCCURS AT A STANDSTILL 0RIOR TO THE ROAD TEST INSPECT THE FOLLOWING
/BSERVE THE FOLLOWING GUIDELINES WHEN PREPARING FOR THE ROAD TEST
s 4IRES 0RESSURE n )NmATED TO SPECIlCATION 7EAR n #UPPING mAT SPOTS FEATHERING AND SHOULDER WEAR 4READ GROOVES n #ORRECT DEPTH OVER ENTIRE SURFACE 4YPE n 4HE TIRE IS THE PROPER APPLICATION &OREIGN DEBRIS n 3TONES MUD ETC s 7HEELS .OT DEFORMED OR BENT 7EIGHTS n 0ROPERLY INSTALLEDCORRECT SIZE 7HEEL BOLTS n 4ORQUED TO SPECIlCATION 4IRE BEAD n 5NIFORM s $RIVELINE .OT DAMAGED OR BENT 0ROPERLY MOUNTED AND SUPPORTED 0ROPERLY ALIGNED s %NGINE "ELTS AND ACCESSORIES FOR DAMAGE 0ROPERLY ALIGNED -OUNTS s %XHAUST .OT DAMAGED OR BENT 0ROPERLY ALIGNED
s #HECK THE CUSTOMER REPAIR ORDER BEFORE BEGINNING THE ROAD TEST )T IS IMPORTANT TO KNOW WHICH SPECIlC CONCERN THE CUSTOMER HAS WITH HISHER VEHICLE 4HIS PREVENTS CORRECTING THE WRONG CONCERN AND INCREASING THE COST OF THE REPAIR )F POSSIBLE ROAD TEST WITH THE CUSTOMER s $ONT BE MISLED BY THE REPORTED LOCATION OF THE NOISE OR VIBRATION 4HE CAUSE ACTUALLY MAY BE SOME DISTANCE AWAY s 2EMEMBER THAT THE VIBRATING BODY MAY GENERATE A SMALL VIBRATION ONLY 4HIS SMALL VIBRATION IN TURN MAY CAUSE A LARGER VIBRATION OR NOISE DUE TO THE VIBRATING BODYS CONTACT WITH OTHER COMPONENTS s #ONDUCT THE ROAD TEST ON A QUIET STREET WHERE SAFELY DUPLICATING THE NOISE OR VIBRATION IS POSSIBLE )T MUST BE POSSIBLE TO OPERATE THE VEHICLE AT THE SPEED IN WHICH THE CONDITION OCCURS )T IS BEST TO CONDUCT THE ROAD TEST ON A ROUTE THAT HAS BEEN PREVIOUSLY DRIVEN WITH KNOWN GOOD VEHICLES 4HIS ALLOWS FOR ANY ROAD IMPERFECTIONS IE ROAD SURFACES AND JOINTS FROM BEING THE SOURCE OF .6( CONCERNS s 4URN OFF THE RADIO AND THE BLOWER FOR THE HEATER AND AIR CONDITIONER UNLESS THE NOISE OR VIBRATION ONLY OCCURS WITH THE AIR CONDITIONING OR RADIO ON s $ETERMINE WHICH TEST EQUIPMENT IS NEEDED FOR THE ROAD TEST )F UTILIZING TEST EQUIPMENT DURING A ROAD TEST IT IS BEST PRACTICE TO HAVE AN ASSISTANT DRIVE WHILE THE EQUIPMENT IS BEING MONITORED AND THE RESULTS RECORDED s &OR COLD WEATHER CLIMATES BE AWARE THAT SNOW AND ICE CAN BE THE CAUSE OF .6( CONCERNS
0ROPERLY MOUNTED AND SUPPORTED
$IAGNOSIS 2OAD 4ESTING 4HE FOLLOWING ROAD TEST PROCEDURE ASSISTS IN CLASSIFYING AN .6( CONCERN INTO s %NGINE SPEED s 6EHICLE SPEED s 7HEEL SPEED %ACH OF THE FOLLOWING PROCEDURES HELPS TO ELIMINATE POSSIBLE COMPONENTS $EPENDING UPON THE CAUSE OF THE .6( CONCERN CERTAIN PROCEDURES MAY OR MAY NOT BE NECESSARY
3LOW !CCELERATION 4EST 4HE lRST VEHICLE CHECK TO DETERMINE A RELATED SYMPTOM OF AN .6( CONCERN IS THE SLOW ACCELERATION TEST 4HIS TEST IS USED TO IDENTIFY THE NOISE OR VIBRATION IF A ROAD TEST WITH THE CUSTOMER WAS NOT POSSIBLE 4HE STEPS OF THE SLOW ACCELERATION TEST ARE 3LOWLY ACCELERATE THE VEHICLE TO THE SPEED IN WHICH THE PROBLEM OCCURS .OTE THE VEHICLE SPEED AND THE ENGINE RPM
s 3LOW !CCELERATION 4EST
)F POSSIBLE DETERMINE THE FREQUENCY OF THE NOISE OR VIBRATION
s .EUTRAL #OAST $OWN 3PEED 4EST
#LASSIFY THE NOISE OR VIBRATION
s $OWNSHIFT 3PEED 4EST s 4ORQUE #ONVERTER 4EST s 3TEERING )NPUT 4EST s 3TEERING )NPUT 4EST s .EUTRAL 2UN 5P 4EST s %NGINE ,OADED 4EST s %NGINE !CCESSORY 4EST
$IAGNOSIS .EUTRAL #OAST $OWN 3PEED 4EST
$OWNSHIFT 3PEED 4EST
4HE NEXT VEHICLE CHECK WHEN PERFORMING THE ROAD TEST IS THE NEUTRAL COAST DOWN SPEED TEST 4HIS TEST DIVIDES THE POSSIBLE CAUSES OF THE NOISE OR VIBRATION INTO TWO CATEGORIES
4HIS VEHICLE CHECK HELPS TO CONlRM THE .6( CONCERN AS ENGINE SPEED RELATED 4HE STEPS OF THE DOWNSHIFT SPEED TEST ARE
s 6EHICLE SPEED RELATED s %NGINE SPEED RELATED s 7HEEL SPEED RELATED 4HE STEPS OF THE NEUTRAL COAST DOWN SPEED TEST ARE $RIVE THE VEHICLE AT A SPEED HIGHER THAN THE SPEED IN WHICH THE NOISE OR VIBRATION WAS OBVIOUS IN THE SLOW ACCELERATION TEST 0LACE THE VEHICLE IN .EUTRAL AND COAST DOWN THROUGH THE SPEED WHERE THE CONCERN OCCURS #LASSIFY THE .6( CONCERN AS EITHER VEHICLE SPEED RELATED OR ENGINE SPEED RELATED s )F THE NOISE OR VIBRATION EXISTS THEN THE CONCERN IS VEHICLE OR WHEEL SPEED RELATED 4HIS ELIMINATES THE ENGINE AND TORQUE CONVERTER AS POSSIBLE CAUSES s )F THE .6( CONCERN DID NOT OCCUR DURING THE NEUTRAL COAST DOWN SPEED TEST PERFORM A DOWNSHIFT SPEED TEST TO CONlRM THE CONCERN AS ENGINE SPEED RELATED
3TOP THE VEHICLE AND PLACE THE TRANSMISSION IN A LOWER GEAR $RIVE THE VEHICLE AT THE ENGINE RPM IN WHICH THE NOISE OR VIBRATION OCCURS s )F THE NOISE OR VIBRATION EXISTS THEN THE CONCERN IS ENGINE SPEED RELATED 4HIS ELIMINATES TIRES WHEELS BRAKES AND SUSPENSION COMPONENTS s )F NECESSARY REPEAT THE TEST USING OTHER GEARS AND .EUTRAL TO CONlRM THE RESULTS
4ORQUE #ONVERTER 4EST 4HIS VEHICLE CHECK DETERMINES HOW THE TORQUE CONVERTER CONTRIBUTES TO AN ENGINE SPEED RELATED CONDITION 4HE STEPS OF THE TORQUE CONVERTER TEST ARE $RIVE THE VEHICLE AT THE SPEED IN WHICH THE .6( CONCERN EXISTS /PERATE THE TORQUE CONVERTER BY TAKING IT IN AND OUT OF LOCK UP BY LIGHTLY DEPRESSING THE BRAKE PEDAL WHILE MAINTAINING VEHICLE SPEED #HECK FOR NOISE WHEN THE TORQUE CONVERTER IS NOT LOCKED UP
$IAGNOSIS 3TEERING )NPUT 4EST
3TEERING )NPUT 4EST
4HE NEXT ROAD TEST STEPS ARE THE TWO STEERING INPUT TESTS 4HESE TESTS DETERMINE IF THE WHEEL BEARINGS AND OTHER SUSPENSION COMPONENTS ARE CONTRIBUTING TO A SPEED RELATED CONDITION
0ERFORM THE 3TEERING )NPUT 4EST IF THE .6( CONDITION OCCURS WHEN TURNING ONLY 4HE STEPS OF 3TEERING )NPUT 4EST ARE
4HE STEPS OF THE 3TEERING )NPUT 4EST ARE $RIVE THE VEHICLE AT THE SPEED IN WHICH THE .6( CONCERN EXISTS -AKE WIDE SWEEPING TURNS IN BOTH DIRECTIONS s )F THE CONCERN GOES AWAY OR GETS WORSE WHEEL BEARINGS HUBS 5NIVERSAL *OINTS 5 JOINTS DRIVE AXLES CONSTANT VELOCITY JOINTS AND TIRE TREAD WEAR MAY BE THE COMPONENTS CAUSING THE CONCERN
$RIVE THE VEHICLE AT A SPEED HIGHER THAN THE SPEED AT WHICH THE NOISE OR VIBRATION OCCURS 0LACE THE VEHICLE IN .EUTRAL AND COAST DOWN THROUGH THE SPEED WHERE THE .6( CONCERN IS OBVIOUS WHILE MAKING WIDE SWEEPING TURNS IN BOTH DIRECTIONS s )F THE CONCERN EXISTS CHECK FOR WORN WHEEL BEARINGS SUSPENSION BUSHINGS CONSTANT VELOCITY JOINTS AND 5 JOINTS CONTAINED IN THE AXLES OF QUATTRO APPLICATIONS s )F THE VIBRATION DOES NOT OCCUR STOP THE VEHICLE AND ENGAGE THE TRANSMISSION TRANSAXLE !LTERNATELY ACCELERATE AND DECELERATE THROUGH THE SPEED AT WHICH THE .6( CONCERN APPEARS WHILE MAKING WIDE SWEEPING TURNS IN BOTH DIRECTIONS s )F THE CONCERN RETURNS THEN THE CAUSE IS DEPENDENT UPON ENGINE LOAD 4HE PROBABLE CAUSES ARE CONSTANT VELOCITY JOINTS OR 5 JOINTS CONTAINED IN THE AXLES OF QUATTRO APPLICATIONS AND LOOSE OR MISSING LUGNUTS s )F THE NOISE IS A hCLUNKING SOUND v ENGINE AND TRANSAXLE MOUNTS SUSPENSION BUSHINGS AND 5 JOINTS ARE PROBABLE CAUSES
$IAGNOSIS .EUTRAL 2UN 5P 4EST 0ERFORM THE .EUTRAL 2UN 5P 4EST IF THE .6( 4HE STEPS OF THE %NGINE ,OADED 4EST ARE CONCERN IS ENGINE SPEED RELATED 5SE THE TEST AS A FOLLOW UP TO THE DOWNSHIFT TEST OR WHEN THE "LOCK THE FRONT AND BACK WHEELS .6( CONCERN OCCURS AT IDLE 4HE STEPS ARE !PPLY THE PARKING AND SERVICE BRAKES )NCREASE THE ENGINE RPM WHILE IN 0ARK OR .EUTRAL
0UT THE TRANSMISSION IN $RIVE WHILE KEEPING THE BRAKES APPLIED
)F NECESSARY MAKE NOTE OF THE RPM AND FREQUENCY OF THE .6( CONCERN
)NCREASE THE ENGINE RPM TO THE RPM AT WHICH THE .6( CONCERN OCCURRED )F NECESSARY MAKE NOTE OF THE RPM AND FREQUENCY OF THE .6( CONCERN
%NGINE ,OADED 4EST 0ERFORM THE %NGINE ,OADED 4EST IF THE .6( CONCERN IS ENGINE SPEED RELATED 4HIS TEST MAY HELP REPRODUCE ENGINE SPEED RELATED CONCERNS NOT EVIDENT WITH THE NEUTRAL RUN UP OR NEUTRAL COAST DOWN SPEED TESTS 4HE ENGINE LOADED TEST ALSO IDENTIlES NOISE AND VIBRATION SENSITIVE TO ENGINE LOAD OR TORQUE 4HESE .6( CONCERNS OFTEN APPEAR DURING HEAVY ACCELERATION OR WHEN CLIMBING A HILL 7ARNING "LOCK THE FRONT AND BACK WHEELS OR INJURY TO PERSONNEL MAY RESULT $O NOT EXCEED lVE SECONDS WHEN PERFORMING THE ENGINE LOADED TEST OR DAMAGE TO THE TRANSMISSION TRANSAXLE MAY RESULT
2ETURN ENGINE TO IDLE 0UT THE TRANSMISSION IN 2EVERSE WHILE KEEPING THE BRAKES APPLIED )NCREASE THE ENGINE RPM TO THE RPM AT WHICH THE .6( CONCERN OCCURRED )F NECESSARY MAKE NOTE OF THE RPM AND FREQUENCY OF THE .6( CONCERN )MMEDIATELY AFTER ENGINE LOADED TEST RUN IN NEUTRAL FOR MINUTES AT A SLIGHTLY ELEVATED RPM TO COOL THE TRANSMISSION
)F THE CONCERN IS DElNITELY ENGINE SPEED RELATED PERFORM THE %NGINE !CCESSORY 4EST TO NARROW DOWN THE POSSIBLE SOURCE OF THE CONCERN
$IAGNOSIS %NGINE !CCESSORY 4EST 0ERFORM THE %NGINE !CCESSORY 4EST IF THE .6( CONCERN IS ENGINE SPEED RELATED 4HIS TEST HELPS LOCATE FAULTY BELTS AND ACCESSORIES THAT ARE CAUSING ENGINE SPEED RELATED .6( CONCERNS 4HE STEPS ARE "LOCK THE FRONT AND BACK WHEELS !PPLY THE PARKING AND SERVICE BRAKES 2EMOVE THE ACCESSORY DRIVE BELTS )NCREASE ENGINE RPM TO THE RPM AT WHICH THE .6( CONCERN OCCURRED s )F THE VIBRATION OCCURS THE BELTS AND ACCESSORIES ARE NOT THE SOURCE OF THE CONCERN s )F THE BELTS AND ACCESSORIES ARE THE SOURCE OF THE .6( CONCERN CONTINUE TO ADD OR REMOVE SPECIlC ACCESSORY BELTS TO LOCATE THE CONCERN
#AUTION 7ITH THE ACCESSORY BELT REMOVED s $O NOT DRIVE THE VEHICLE s $O NOT OPERATE THE ENGINE FOR EXTENDED PERIODS n 7ATER COOLED ALTERNATORS CAN FAIL n %NGINES CAN OVERHEAT
.OTES
%NGINE 6IBRATIONS %NGINE 3PEED 2ELATED 6IBRATIONS
4YPES OF %NGINE 6IBRATIONS
$URING THE INITIAL VEHICLE ROAD TEST USING THE ROAD TEST PROCEDURE THE VIBRATION CAUSING THE CONCERN WILL BE CLASSIlED INTO EITHER ENGINE SPEED RELATED OR VEHICLE SPEED RELATED 4HIS SECTION WILL BE USED WHEN THE VIBRATION IS FOUND TO BE ENGINE SPEED RELATED
-ANY .6( CONCERNS ARE RELATED TO THE ENGINE SYSTEMS 4HE OPERATION OF THE ENGINE CREATES A NATURAL VIBRATION )F ANY ONE COMPONENT IS SLIGHTLY OUT OF BALANCE THE NATURAL VIBRATION OF THE ENGINE IS COMPOUNDED %NGINE VIBRATION IS GENERALLY CAUSED BY ANY OF THE FOLLOWING
%NGINE SPEED RELATED VIBRATIONS ARE CAUSED BY A COMPONENT THAT IS DRIVEN BY THE ENGINE 4HESE COMPONENTS MAY BE PART OF THE ENGINE ASSEMBLY OR AN ENGINE ACCESSORY 5SING THE FREQUENCY OF THE VIBRATION AND MATHEMATICAL FORMULAS THE ENGINE SPEED RELATED VIBRATION CAN BE CLASSIlED INTO THESE CATEGORIES s %NGINE #OMPONENTS s %NGINE !CCESSORIES s %NGINE #YLINDERS &IRING &REQUENCY
s &IRST AND SECOND ORDER ENGINE IMBALANCE s %NGINE lRING FREQUENCY s %NGINE MOUNTS s %NGINE ACCESSORIES &IRST AND 3ECOND /RDER %NGINE )MBALANCE ! lRST ORDER ENGINE IMBALANCE IS CREATED WHEN ANY COMPONENT THAT ROTATES AT CRANKSHAFT SPEED IS OUT OF BALANCE OR HAS EXCESSIVE RUNOUT %XAMPLES ARE HARMONIC BALANCER mYWHEEL OR TORQUE CONVERTER IMBALANCE AND CYLINDER TO CYLINDER MASS DIFFERENCES )N RARE CASES THE CRANKSHAFT ITSELF MAY BE IMBALANCED "ALANCING THE COMPONENT OR CORRECTING THE RUNOUT MAY BRING THE VIBRATION TO AN ACCEPTABLE LEVEL &IRST ORDER ENGINE VIBRATIONS CAN BE OFFSET BY PROPER ARRANGEMENT OF CRANKSHAFT COUNTERWEIGHTS 3ECOND ORDER ENGINE IMBALANCE IS CAUSED BY THE UP AND DOWN MOTION OF THE PISTONS 4HIS REVERSAL OF MASS AND MOTION CREATES A NATURAL VIBRATION 3YMPTOMS OF ENGINE IMBALANCE INCLUDE s ! LOW SPEED SHAKE FELT BETWEEN AND RPM THAT HAS A FREQUENCY OF TO (Z s ! ROUGHNESS SOMETIMES FELT AND HEARD BETWEEN TO RPM AT A FREQUENCY OF TO (Z &IRST AND SECOND ORDER ENGINE IMBALANCES ARE USUALLY DETECTED DURING THE .EUTRAL 2UN 5P 4EST
%NGINE 6IBRATIONS (ALF /RDER %NGINE 6IBRATION ! HALF ORDER VIBRATION IS CREATED WHEN ANY COMPONENT THAT ROTATES AT HALF THE CRANKSHAFT SPEED IS OUT OF BALANCE OR HAS EXCESSIVE RUNOUT !N EXAMPLE OF THIS IS CAMSHAFT IMBALANCE "ALANCING THE COMPONENT OR CORRECTING THE RUNOUT MAY BRING THE VIBRATION TO AN ACCEPTABLE LEVEL
4ORQUE CONVERTER IMBALANCE IS ALSO A POSSIBILITY WHEN DEALING WITH AN ENGINE DEPENDENT .6( CONCERN !LTHOUGH RARE ON NEW VEHICLES THIS TYPE OF VIBRATION MAY APPEAR IF THE TORQUE CONVERTER HAD BEEN REPLACED OR INSTALLED INCORRECTLY DURING TRANSMISSION SERVICE !LSO INSPECT THE mEXPLATE FOR DAMAGE AS THIS COULD CAUSE NOISE OR VIBRATION
4ORQUE #ONVERTER !LTHOUGH NOT ACTUALLY AN ENGINE COMPONENT THE TORQUE CONVERTER ROTATES AT ENGINE SPEED AND ITS VIBRATION FREQUENCIES ARE OFTEN THE SAME AS THE ENGINE 4HE TORQUE CONVERTER IS A mUID COUPLING THAT USES TRANSMISSION mUID TO TRANSFER AND MULTIPLY ENGINE TORQUE TO THE INPUT SHAFT OF AN AUTOMATIC TRANSMISSION
4ORQUE #ONVERTER
4HE MOVEMENT OF THE mUID BETWEEN THE IMPELLER WHICH IS CONNECTED TO THE ENGINE AND THE TURBINE WHICH CONNECTS TO THE TRANSMISSION CAN SOMETIMES GENERATE A BEAT SOUND )F THIS IS THE CASE HOWEVER THE SOUND DISAPPEARS WHEN THE TORQUE CONVERTER CLUTCH ENGAGES MECHANICALLY LOCKING THE IMPELLER AND TURBINE TOGETHER !NOTHER .6( CONCERN THAT MAY BE CAUSED BY THE TORQUE CONVERTER IS VIBRATION DURING CLUTCH ENGAGEMENT )F THE CONVERTER CLUTCH DOES NOT APPLY SMOOTHLY IT MIGHT RESULT IN A JERKING OR SHAKING VIBRATION THAT CAN BE FELT THROUGHOUT THE VEHICLE 4HIS VIBRATION DISAPPEARS WHEN THE CLUTCH lNALLY ENGAGES COMPLETELY
#ONVERTER CLUTCH VIBRATIONS ALSO CAN OCCUR DURING DOWNSHIFTS AND COASTING IF THE CLUTCH FAILS TO RELEASE CORRECTLY )F A CONVERTER CLUTCH MALFUNCTION IS THE SUSPECTED CAUSE OF AN .6( CONCERN REFER TO THE APPROPRIATE SERVICE PUBLICATIONS FOR TRANSMISSION DIAGNOSTIC PROCEDURES
%NGINE 6IBRATIONS %NGINE -OUNTS 4HE lRST COMPONENTS THAT ISOLATE VIBRATION FROM THE ENGINE TO THE PASSENGER COMPARTMENT ARE ENGINE MOUNTS %NGINE AND TRANSMISSION MOUNTING CONSISTS OF A NUMBER OF RELATIVELY SMALL PARTS AND ARE SOMETIMES IGNORED WHEN TROUBLESHOOTING (OWEVER THESE PARTS ARE EXTREMELY IMPORTANT IN PREVENTING NOISE AND VIBRATION PRODUCED BY THE ENGINE 4ORQUE REACTION FORCE OF THE ENGINE ACTS DIRECTLY ON THE TRANSMISSION CAUSING ENGINE MOUNTS TO BE SUBJECTED TO A LARGE FORCE 4HEREFORE ENGINE MOUNTS MUST BE RIGID TO STABILIZE THE ENGINE /N THE OTHER HAND TO MINIMIZE INHERENT ENGINE VIBRATIONS AND NOISE DURING ALL ENGINE SPEEDS THE ENGINE MOUNTS ALSO MUST BE SOFT !NY FAULT IN THE ENGINE MOUNTING SYSTEM CAN LEAD DIRECTLY TO NOISE AND VIBRATION )NSPECT ENGINE MOUNTS FOR CRACKS OR DAMAGE TO THE INSULATOR AND THE BRACKET 'ROUNDED THE ENGINE MOUNTED BRACKET CONTACTING THE FRAME MOUNTED BRACKET OR STRAINED ENGINE MOUNTS MAY NOT ISOLATE ENGINE VIBRATIONS %LECTRO (YDRAULIC %NGINE -OUNT
%NGINE MOUNTS MUST BE INSTALLED CORRECTLY )F THE MOUNTS ARE INSTALLED INCORRECTLY OR INCORRECT PARTS ARE USED THEY CANNOT ABSORB ENGINE VIBRATION 4HE 23 ENGINE MOUNTS USE SEVERAL MOUNTING HOLES DEPENDING ON WHICH ENGINE OPTION IS INSTALLED IN THE VEHICLE 3ERVICE INFORMATION DETAILS THE PROCEDURE TO REMOVE AND INSTALL THE ENGINE MOUNTING BOLTS AND LOCATOR PINS 3EVERAL !UDI MODELS USE %LECTRO (YDRAULIC %NGINE -OUNT 3OLENOID 6ALVES 4HESE VALVES SOFTEN OR STIFFEN THE ENGINE MOUNTS DEPENDING UPON ENGINE OPERATING CHARACTERISTICS 4HE SYSTEM MAY BE THE SOURCE OF AN ENGINE VIBRATION AT IDLE IF NOT OPERATING PROPERLY #ONSULT !UDI SERVICE INFORMATION FOR DIAGNOSTIC PROCEDURES FOR THIS SYSTEM
%NGINE 6IBRATIONS !CCESSORY 6IBRATION %NGINE ACCESSORIES CAN BE A SOURCE OF ENGINE VIBRATION &OR EXAMPLE AIR CONDITIONING COMPRESSORS ARE SUSCEPTIBLE TO OVERCHARGING WHICH CAN RESULT IN AN .6( CONDITION !CCESSORY PULLEY MISALIGNMENT OR FAULTY COMPONENTS ALSO CAN CAUSE VIBRATIONS 7ITH THE ADVENT OF SERPENTINE BELTS IT IS NO LONGER POSSIBLE TO REMOVE BELTS ONE AT A TIME TO ISOLATE THE SOURCE COMPONENT "ECAUSE THE SERPENTINE BELT DRIVES ALL COMPONENTS ONE COMPONENT MAY AFFECT ANOTHER THROUGH RESONANCE )F REMOVING THE SERPENTINE BELT ELIMINATES THE VIBRATION REINSTALL THE BELT AND OPERATE EACH COMPONENT SEPARATELY "Y TURNING THE AIR CONDITIONING /. AND /&& OR BY TURNING THE STEERING WHEEL SOME COMPONENTS CAN BE ELIMINATED OR ISOLATED AS .6( SOURCES 7HEN DIAGNOSING ACCESSORY VIBRATION MAKE SURE THE SOURCE OF THE VIBRATION IS NOT CAUSED BY THE ENGINE OR ENGINE lRING FREQUENCIES %NGINE lRING FREQUENCIES CAN CAUSE COMPONENTS TO RESONATE AND VIBRATE 4HE VIBRATION AMPLITUDE MAY INCREASE WITH THE ACCESSORIES LOADED 4HE MOST EFFECTIVE REPAIR MAY BE ISOLATING THE DISTURBANCE BY INTERRUPTING ITS TRANSFER PATH RATHER THAN ATTEMPTING TO ELIMINATE THE SOURCE
%NGINE 6IBRATIONS %NGINE 6IBRATION &ORMULA &OR PURPOSES OF VIBRATION DIAGNOSIS THE ENGINE ALSO INCLUDES THE TORQUE CONVERTER AND EXHAUST SYSTEM 7HEN AN .6( PROBLEM IS TORQUE SENSITIVE THE VIBRATION MAY APPEAR OR DISAPPEAR AT DIFFERENT VEHICLE SPEEDS MPHKPH BUT IS PRESENT AT THE SAME ENGINE RPM &OR EXAMPLE IF A VEHICLE HAS SOME VIBRATION AT MPH KPH MPH KPH AND MPH KPH BUT IS WORSE AT A PARTICULAR SPEED THE .6( CONCERN IS PROBABLY TORQUE SENSITIVE SINCE THE CONDITION OCCURS AT THE SAME ENGINE RPM BUT AT A DIFFERENT LOAD 5SE THE ENGINE RPM AT WHICH THE .6( SYMPTOM OCCURS TO DETERMINE ENGINE FREQUENCY #ALCULATE ENGINE FREQUENCY AS FOLLOWS $IVIDE THE ENGINE RPM BY THE NUMBER OF SECONDS IN A MINUTE RP M ( Z E N G I N E F RE Q U E N C Y &OR EXAMPLE IF THE CORRESPONDING ENGINE RPM OF AN .6( PROBLEM ON A VEHICLE IS RPM THE RESULTING ENGINE FREQUENCY IS (Z
(Z 4O GET THE SECOND AND THIRD ORDER FREQUENCY MULTIPLY THE lRST ORDER FREQUENCY BY FOR SECOND ORDER FOR THIRD ORDER ETC &IRST ORDER X 3ECOND ORDER & I R S T O R D E R X 4 H I R D O R D E R %NGINE VIBRATIONS ALSO MAY HAVE HALF ORDER FREQUENCIES HALF ORDER FREQUENCIES ARE CALCULATED BY DIVIDING THE lRST ORDER BY &IRST ORDER (ALF ORDER
%NGINE 6IBRATIONS %NGINE !CCESSORY &ORMULA "ELT DRIVEN ENGINE ACCESSORIES PRODUCE VIBRATIONS AT DIFFERENT FREQUENCIES THAN THE ENGINE ITSELF 4HIS IS BECAUSE THE DRIVE RATIO CREATED BY THE DIFFERENT SIZE PULLEYS CAUSES THEM TO ROTATE AT DIFFERENT SPEEDS $ETERMINING ENGINE ACCESSORY FREQUENCY IS COMPARABLE TO CALCULATING DRIVELINE FREQUENCY #ALCULATE ENGINE ACCESSORY FREQUENCY BY PERFORMING THE FOLLOWING STEPS $ETERMINE THE SIZE RATIO BETWEEN THE ACCESSORY PULLEY AND THE CRANKSHAFT PULLEY BY DIVIDING THE CRANKSHAFT PULLEY DIAMETER BY THE ACCESSORY PULLEY DIAMETER # R A N K S H A FT P U L L E Y D I A M E T E R !CCESSORY PULLEY DIAMETER 0ULLEY RATIO &OR EXAMPLE IF THE DIAMETER OF THE CRANKSHAFT PULLEY IS MM INCHES AND THE ACCESSORY PULLEY DIAMETER IS MM INCHES DIVIDE BY 4HE ACCESSORY PULLEY ROTATES THREE TIMES FOR EVERY CRANKSHAFT ROTATION
-ULTIPLY THE ENGINE RPM IN WHICH THE .6( CONDITION OCCURS BY THE PULLEY RATIO % N G I N E RP M X 0 U L L E Y R A T I O ! C C E S S O R Y RP M &OR EXAMPLE IF THE ENGINE RPM IS RPM ENGINE SPEED MULTIPLY BY 4HE ACCESSORY IS ROTATING AT RPM X RP M $IVIDE THE ACCESSORY RPM BY THE NUMBER OF SECONDS IN A MINUTE TO OBTAIN THE ACCESSORY (Z ! C C E S S O R Y RP M ! C C E S S O R Y ( Z &OR EXAMPLE THE ENGINE ACCESSORY RPM IS DIVIDE BY 4HE ENGINE ACCESSORY FREQUENCY IS (Z (Z
! C C E S S O R Y ( Z
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%NGINE 6IBRATIONS 4YPES OF %NGINE .OISES 7HEN ENGINE COMPONENTS DEVIATE FROM THE PRECISE SPECIlCATIONS IN WHICH THEY WERE ENGINEERED THE ENGINE CREATES EXCESSIVE OR INTOLERABLE NOISES 2ECIPROCATING MOTION OF THE PISTONS AND THE ROTATING MOTION OF OTHER ENGINE COMPONENTS CREATE INHERENT NOISES #AUSES OF ENGINE NOISES INCLUDE
!BNORMAL #OMBUSTION !NY ABNORMALITIES IN THE COMBUSTION PROCESS CAN LEAD TO AUDIBLE ENGINE VIBRATIONS !BNORMAL COMBUSTION CAN INCLUDE ANY OF THE FOLLOWING s 3PARK KNOCK PINGING s "ACKlRING
s #OMBUSTION n .OISES ARE PRODUCED WHEN $ETONATION 0INGING THE AIRFUEL MIXTURE IS IGNITED 0INGING IS GENERALLY DISTINGUISHED BY A HIGH s &RICTION PITCHED STRIKING NOISE GENERATED WHEN THE THROTTLE IS FULLY OPEN OR DURING HARD ACCELERATION s -OVING PARTS AND THE IMPACT BETWEEN )F OPERATION IS CONTINUED IN THIS STATE THE RECIPROCATING PARTS PISTONS AND VALVES ARE ADVERSELY AFFECTED s 4OLERANCE hSLAPv n 0ISTONS MOVE UP AND RESULTING IN A DAMAGED ENGINE DOWN AND THE TOLERANCE BETWEEN PARTS IS REPEATEDLY PULLED IN ALTERNATING DIRECTIONS #AUSES OF ENGINE SPARK KNOCK PINGING INCLUDE THE FOLLOWING s )NADEQUATE FUEL s )NCORRECT TIMING s #ARBON DEPOSITS IN THE COMBUSTION CHAMBER
%NGINE 6IBRATIONS "ACKlRING
%XHAUST .OISE
/NE TYPE OF BACKlRE KNOWN AS POP BACK OCCURS 4HE EXHAUST SYSTEM CAN BE A SOURCE OF NOISE WHEN THE CYLINDER IS lRED BEFORE THE INTAKE %XHAUST NOISES INCLUDE VALVE CLOSES 7HEN THE INTAKE VALVE OPENS THE AIRFUEL MIXTURE IN THE INTAKE MANIFOLD IS IGNITED s %XHAUST GAS SOUNDS AND BURNS 4HIS SITUATION IS SOMETIMES VIOLENT s -UFmER AND PIPE ENOUGH TO CAUSE AN EXPLOSIVE REPORT WITHIN THE MANIFOLD 0OP BACK CAN BE CAUSED BY THE FOLLOWING %XHAUST GAS SOUNDS ARE FURTHER SUBDIVIDED INTO THREE CATEGORIES s %XCESSIVELY LEAN FUEL MIXTURE s )NCORRECT VALVE TIMING
s 0ULSATING s !IR COLUMN RESONANCE
)F THE MIXTURE IS TOO LEAN mAME SPEED s !IR STREAM SOUNDS BECOMES SLOWER TAKING LONGER TO COMPLETE THE COMBUSTION PROCESS )F TIMING HAS BEEN DISTURBED A POP BACK CAN OCCUR AND POSSIBLY THE %XHAUST GASES ARE DISCHARGED EACH TIME THE EXHAUST VALVES OPEN CREATING A PULSATING SOUND ENGINE WILL NOT START 4HE SOUND IS CYCLIC AND IS ASSOCIATED WITH !NOTHER TYPE OF BACKlRE IS AFTERlRE !FTERlRE IS ENGINE SPEED AND THE NUMBER OF CYLINDERS 4HE COMBUSTION IN THE EXHAUST SYSTEM PRODUCING A SOUND IS RELATIVELY LOW PITCHED CONSISTING MAINLY LOUD REPORT OR mAMES AT THE TAIL PIPE #ONDITIONS OF THIS BASIC FREQUENCY THAT CAN PRODUCE AFTERlRE ARE !IR COLUMN RESONANCE CONSISTS OF SOUNDS s $RIVING FOR PERIODS OF TIME WITH THE PRODUCED IN EXHAUST PIPES AND MUFmERS 0IPE ENGINE BRAKED LENGTH AND THE CROSS SECTIONAL AREA OF THE PIPE DETERMINE THE FREQUENCY !IR STREAM SOUNDS CAN s 4HE THROTTLE VALVE CLOSING RAPIDLY BE PRODUCED BY HIGH SPEED EXHAUST !N EXAMPLE OF THIS IS TURBULENCE CAUSED BY AIR GOING THROUGH !FTERlRE OCCURS WHEN UNBURNED FUEL IS RELEASED THE MUFmER OR JET NOISE WHEN EXHAUST IS DISCHARGED FROM THE TAILPIPE FROM THE COMBUSTION CHAMBER AND IS REHEATED BY COMPONENTS IN THE EXHAUST SYSTEM 7HEN -UFmER AND EXHAUST NOISES CAN BE CAUSED THE FUEL IS REHEATED PAST ITS SELF IGNITION POINT BY EXHAUST SYSTEM MISALIGNMENT INCORRECTLY AFTERlRE OCCURS )N SOME CASES AFTERlRE INSTALLED OR DAMAGED MOUNTING BRACKETS OR CAN CAUSE DAMAGE TO THE MUFmER CATALYTIC FAILED HANGERS 4HIS CAN CAUSE A VARIETY OF CONVERTER OR OTHER COMPONENTS OF THE EXHAUST ANNOYING NOISES THAT CAN BE LOCATED WITH A SYSTEM -AIN CAUSES OF AFTERlRE INCLUDE THOROUGH VISUAL INSPECTION s 2ICH FUEL MIXTURE s )NCORRECT IGNITION OR VALVE TIMING s &AULTY IGNITION COMPONENTS
!NY OF THESE SOUNDS IN THE EXHAUST SYSTEM CAN BE CARRIED OR TRANSMITTED THROUGHOUT MANY OF THE EXHAUST SYSTEM COMPONENTS AND INTO THE PASSENGER COMPARTMENT
%NGINE 6IBRATIONS #OMPELLING &ORCE OF %XHAUST
%XHAUST (ANGERS
4HE COMPELLING FORCE OF EXHAUST EXITING EACH CYLINDER CREATES A PULSATION ON THE EXHAUST MANIFOLD 4HE PULSATING PRESSURE AT THE EXHAUST MANIFOLD PRODUCES ACOUSTIC ENERGY WHICH IS TRANSMITTED TO THE EXHAUST PIPE 4HE PULSATING SOUND WAVES TRAVELING THROUGH THE EXHAUST PIPE ARE A SOURCE OF VIBRATION FOR THE EXHAUST SYSTEM %XHAUST VIBRATIONS CAN BECOME AMPLIlED BY RESONATING WITH ENGINE lRING FREQUENCIES AND VIBRATIONS CAUSED BY THE RECIPROCAL MOTION OF THE PISTONS 4HE COMBINATION OF THESE VIBRATIONS CAN PRODUCE UNWANTED .6( CONCERNS
4HE COMBINATION OF ENGINE EXHAUST AND ACOUSTIC VIBRATIONS WITHIN THE EXHAUST SYSTEM MUST BE DAMPENED )N ORDER TO DAMPEN THESE VIBRATIONS AND PREVENT THEM FROM ACTING ON THE BODY OF THE VEHICLE EXHAUST HANGERS MUST BE SPECIALLY DESIGNED %XHAUST HANGERS ARE DESIGNED TO SUSPEND THE EXHAUST PIPE FROM THE BODY AND TO PREVENT TRANSMISSION OF VIBRATION TO THE BODY %XHAUST HANGERS USUALLY CONSIST OF RIGID METAL TO SUPPORT THE SYSTEM SEPARATED BY RUBBER TO DAMPEN THE VIBRATION )DEALLY HANGERS SHOULD BE LOCATED FOR SUPPORT AT POINTS WHERE THEY BEAR THE WEIGHT OF THE EXHAUST UNIFORMLY 4HEY ARE ALSO LOCATED AT POINTS OF INHERENT MINIMUM VIBRATION 4HE LOCATION AND TENSION OF THE HANGER RUBBER AFFECTS THE PASSENGER COMPARTMENT NOISE LEVEL -AIN MUFmER HANGERS ARE DOUBLE VIBRATION PROOF 4HE BODY SIDE OF THE MOUNT IS INSTALLED WITH A RUBBER BRACKET AND THE MUFmER IS THEN SUPPORTED BY A HANGER
%XHAUST &LAP 3OME !UDI 44 ! AND ! MODELS HAVE AN EXHAUST mAP THAT IS CONTROLLED BY THE %NGINE #ONTROL -ODULE %#- 4HIS mAP WILL OPEN OR CLOSE DEPENDING ON EITHER ENGINE SPEED OR OTHER VEHICLE CONDITIONS 7HEN DIAGNOSING AN EXHAUST NOISE OR OTHER .6( CONCERN BE SURE THIS mAP IS OPERATING CORRECTLY AND IS NOT THE CAUSE OF ABNORMAL NOISES
%NGINE 6IBRATIONS %XHAUST 3YSTEM 3YMPTOMS AND #ORRECTIONS %XHAUST SYSTEM VIBRATIONS SYMPTOMS AND POSSIBLE CORRECTIONS ARE LISTED IN THE TABLE
%XHAUST 3YSTEM .6( #ONCERNS #/.$)4)/.
39-04/-
#/22%#4)/.
5NPLEASANT DRONING
'ENERATED WHEN EXHAUST SYSTEM VIBRATION IS TRANSMITTED THROUGH EXHAUST PIPE HANGERS AND ENGINE MOUNTS TO THE BODY #AUSES BODY PANELS AND FRAMES TO VIBRATE
)NSPECT EXHAUST PIPE HANGERS AND ENGINE MOUNTS FOR DAMAGE 4IGHTEN OR REPLACE AS NECESSARY
/UTSIDE PASSENGER COMPARTMENT RADIATING NOISE
.OISE PRODUCED BY VIBRATION OF EXHAUST SYSTEM PIPES MUFmER SHELL END PLATE SEPARATOR EXHAUST PIPE OR SHIELD PLATE %NGINE RACING CAN REPRODUCE THIS NOISE
)DENTIFY EXHAUST COMPONENTS RESPONSIBLE FOR THE NOISE AND CHECK FOR LOOSENESS DAMAGE OR INTERFERENCE !DJUST OR REPLACE AS NECESSARY
)DLING VIBRATION
(EAVY DEFORMATION OF EXHAUST PIPES OR mEXIBLE TUBES COLLAPSED mEXIBLE TUBES CAN CHANGE VIBRATION CHARACTERISTICS OF THE EXHAUST SYSTEM INDUCING IDLING VIBRATION
2EPLACE DAMAGED OR DEFORMED EXHAUST COMPONENT
%NGINE 6IBRATIONS %NGINE &IRING &REQUENCY !LL ENGINES HAVE INHERENT lRST ORDER VIBRATIONS %NGINES ALSO HAVE VIBRATIONS CREATED BY lRING FREQUENCY &IRING FREQUENCY REFERS TO THE FORCE CREATED BY THE ENGINE EACH TIME A CYLINDER lRES 4HE FORCE OF THE COMBUSTION CREATES ONE PULSE AND WITH THE CYLINDERS lRING IN ORDER A NATURAL VIBRATION IS CREATED 4HE HIGHER THE LOAD AN ENGINE IS UNDER THE MORE PROMINENT THE lRING FREQUENCY BECOMES 6IBRATIONS ALSO INCREASE WHEN THE ENGINE HAS A PROBLEM THAT INTERFERES WITH THE NORMAL COMBUSTION CYCLE 3YMPTOMS OF lRING FREQUENCY .6( CONCERNS INCLUDE s %NGINE RPM SENSITIVITY s 4ORQUE SENSITIVITY s ,OW FREQUENCY NOISE s 3HAKE OR BUZZ s ,OADED ENGINE )F AN .6( CONCERN IS lRING FREQUENCY SENSITIVE IT MAY BE CAUSING RESONANCE OF ANOTHER COMPONENT WHEN A SPECIlC RPM IS REACHED &IRING FREQUENCY CONCERNS USUALLY HAVE A NARROW RPM RANGE 4O PREVENT THE VIBRATIONS CREATED BY lRING PULSES FROM BECOMING AN .6( CONCERN THE VIBRATION MUST BE ISOLATED -OTOR MOUNTS ARE DESIGNED TO MINIMIZE THE AMOUNT OF VIBRATIONS THAT REACH THE PASSENGER COMPARTMENT
%NGINE 6IBRATIONS %NGINE &IRING &REQUENCY &ORMULA %NGINE lRING FREQUENCY IS A TERM USED TO DESCRIBE THE PULSES AN ENGINE CREATES FROM THE lRING OF THE CYLINDERS %NGINE lRING FREQUENCY DEPENDS UPON HOW MANY CYLINDERS AN ENGINE HAS 4HE NUMBER OF TIMES AN ENGINE lRES A CYLINDER WITH EACH CRANKSHAFT REVOLUTION IS EQUAL TO ONE HALF THE NUMBER OF CYLINDERS ! FOUR CYLINDER ENGINE lRES TWO CYLINDERS WITH EACH CRANKSHAFT REVOLUTION 4WO REVOLUTIONS OF THE CRANKSHAFT lRES ALL FOUR CYLINDERS ! SIX CYLINDER ENGINE lRES THREE CYLINDERS WITH EACH CRANKSHAFT REVOLUTION !N EIGHT CYLINDER ENGINE lRES FOUR CYLINDERS FOR EACH CRANKSHAFT REVOLUTION #ALCULATE THE ENGINE lRING FREQUENCY BY PERFORMING THE FOLLOWING STEPS $IVIDE THE ENGINE RPM AT WHICH THE VIBRATION OCCURS BY RP M % N G I N E ( Z &OR EXAMPLE RP M ( Z -ULTIPLY ENGINE FREQUENCY BY HALF OF THE NUMBER OF CYLINDERS IN THE ENGINE &OR A FOUR STROKE ENGINE
%NGINE (Z X (ALF THE NUMBER OF C Y L I N D E R S % N G I N E F I RI N G ( Z &OR EXAMPLE X SIX CYLINDER ENGINE % N G I N E & I RI N G ( Z
6EHICLE 3PEED 6IBRATIONS 6EHICLE 3PEED 2ELATED 6IBRATIONS
4IRES AND 7HEELS
$URING THE INITIAL VEHICLE ROAD TEST USING THE ROAD TEST PROCEDURES THE VIBRATION CAUSING THE CONCERN WILL BE CLASSIlED INTO EITHER ENGINE SPEED RELATED OR VEHICLE SPEED RELATED 4HIS SECTION WILL BE USED WHEN THE VIBRATION IS FOUND TO BE VEHICLE SPEED RELATED
.OISE AND VIBRATION THAT OCCUR DURING DRIVING HAVE VARIOUS SOURCES 4HE MAJOR SOURCES ARE THE FOLLOWING
6EHICLE SPEED RELATED VIBRATIONS ARE CAUSED BY A COMPONENT THAT IS ROTATING AT VEHICLE SPEED 4HESE COMPONENTS MAY BE PART OF THE TIRE AND WHEEL ASSEMBLIES OR A DRIVE TRAIN COMPONENT TRANSMITTING POWER TO THE WHEELS 4HERE ARE DRIVE TRAIN COMPONENTS THAT ROTATE AT TIRE AND WHEEL FREQUENCIES IE AXLE SHAFTS OR BRAKE COMPONENTS 4HE VIBRATION CAN BE DIAGNOSED TO ANOTHER COMPONENT ROTATING AT TIRE FREQUENCIES BY SUBSTITUTING TIRES AND WHEELS OF THE SAME TYPE FROM A KNOWN GOOD VEHICLE 4HESE COMPONENTS WILL NEED TO BE DIAGNOSED AFTER A TIRE FREQUENCY VIBRATION CANNOT BE CORRECTED BY SERVICING THE TIRE AND WHEEL ASSEMBLIES 5SING THE FREQUENCY OF THE VIBRATION AND MATHEMATICAL FORMULAS THE VEHICLE SPEED RELATED VIBRATION CAN BE CLASSIlED INTO THESE CATEGORIES
s 2OUGH OR IRREGULAR ROAD SURFACES s #ONDITION OF THE TIRES AND WHEELS )MPACT FORCE CAUSED BY ROUGH AND IRREGULAR ROAD SURFACES IS lRST TRANSMITTED TO THE TIRES CAUSING THEM TO VIBRATE 4HIS CHARACTERISTIC REPRESENTS THE CLOSE RELATIONSHIP THAT EXISTS BETWEEN THE TIRE AND ROAD SURFACE 4IRES JUST LIKE THE SUSPENSION BODY AND OTHER COMPONENTS ARE DESIGNED TO MINIMIZE NOISE AND VIBRATION (OWEVER THEY WEAR FASTER THAN OTHER COMPONENTS 4HIS IS A CONTRIBUTING FACTOR TO TIRE AND WHEEL NOISE AND VIBRATION 4IRES AND WHEELS CAN CAUSE VEHICLE VIBRATIONS FOR ONE OR MORE OF THE FOLLOWING REASONS s )MBALANCE s %XCESSIVE RADIAL FORCE VARIATION s %XCESSIVE RADIAL RUNOUT
s 4IRE AND 7HEEL !SSEMBLY s $RIVE 4RAIN #OMPONENT
s %XCESSIVE LATERAL RUNOUT s )MPROPERLY MOUNTED WHEEL ON THE VEHICLES HUB /NE OR MORE OF THE FOLLOWING TIRE PROPERTIES CAN CAUSE TIRE NOISE s .ATURAL FREQUENCY AND VIBRATION TRANSFER CHARACTERISTICS s 4READ PATTERNS
6EHICLE 3PEED 6IBRATIONS )MBALANCE
3TATIC "ALANCING
7HEN THE TIRE AND WHEEL ASSEMBLY ARE ROTATING AT NORMAL HIGHWAY SPEEDS IMBALANCE CONDITIONS ARE MOST LIKELY TO BE NOTICED BY THE DRIVER AND THE OCCUPANTS OF THE PASSENGER COMPARTMENT 4HE lRST STEP IN CORRECTING A TIRE AND WHEEL VIBRATION IS TO BALANCE THE TIRE AND WHEEL ASSEMBLY 4HERE ARE TWO METHODS FOR BALANCING TIRE AND WHEEL ASSEMBLIES 4HEY ARE
!S THE WORD STATIC IMPLIES THE TIRE WILL BE BALANCED WHEN AT REST &OR EXAMPLE IF AN UNMOVING ASSEMBLY WAS CENTERED ON A CONE AND WAS BALANCED IT WOULD BE STATICALLY BALANCED ! hBUBBLE BALANCERv IS DESIGNED TO STATICALLY BALANCE A TIRE AND WHEEL ASSEMBLY
s 3TATIC "ALANCING s $YNAMIC "ALANCING
3TATIC IMBALANCE IS WHERE THERE IS ONE AMOUNT OF WEIGHT LOCATED IN THE CENTER OF THE TIRE AND WHEEL ASSEMBLY CAUSING AN IMBALANCE !S THE WEIGHT ROTATES CENTRIFUGAL FORCES ARE CREATED CAUSING THE WHEEL TO LIFT AS THE WEIGHT REACHES TOP DEAD CENTER 4HIS LIFTING MOTION CAUSES THE TIRE AND WHEEL ASSEMBLY TO MOVE hUP AND DOWNv CREATING A BOUNCE TO BE FELT 4HE STATIC IMBALANCE CONDITION IS EVIDENT BY A hJIGGLEv OR UP DOWN MOVEMENT OF THE STEERING WHEEL 4HESE VIBRATIONS MAY ALSO BE APPARENT IN THE BODY WITH OR WITHOUT STEERING WHEEL SHAKE ! STATICALLY IMBALANCED TIRE DRIVEN FOR AN EXTENDED PERIOD MAY CAUSE hCUPPINGh IN THE TIRES TREAD CREATE VIBRATION AND ADVERSELY AFFECT HANDLING 3TATIC BALANCING ALONE IS A SELDOM RECOMMENDED PROCEDURE THAT BALANCES THE ASSEMBLY USING ONLY A SINGLE WEIGHT PLANE &OR EXAMPLE A SINGLE WEIGHT IS COMMONLY PLACED ON THE INNER CLIP WEIGHT POSITION FOR COSMETIC PURPOSES 4HIS IS NOT A RECOMMENDED PRACTICE AND USUALLY RESULTS IN AN ASSEMBLY THAT IS NOT DYNAMICALLY BALANCED 4HE ASSEMBLY MAY THEN EXPERIENCE SIDE TO SIDE IMBALANCE WHILE IN MOTION CAUSING A SHIMMY CONDITION AND OBJECTIONABLE VIBRATION
6EHICLE 3PEED 6IBRATIONS $YNAMIC "ALANCING $YNAMIC IMBALANCE IS DElNED WHERE ONE OR MORE LOCATIONS OF THE TIRE AND WHEEL ASSEMBLY ARE HEAVIER CAUSING AN IMBALANCE FORCE OR AN IMBALANCE WOBBLE 4HE EXAMPLE SHOWN IS A TIRE AND WHEEL ASSEMBLY WITH TWO HEAVY SPOTS OF EQUAL WEIGHT WHICH ARE LOCATED DEGREES ACROSS FROM EACH OTHER ON OPPOSITE SIDES !S THIS ASSEMBLY ROTATES CENTRIFUGAL FORCES CAUSE A LARGE IMBALANCE WOBBLE TO BE CREATED BUT THE IMBALANCE FORCE AS WELL AS THE STATIC IMBALANCE WILL BE ZERO ! WHEEL WITH THIS CONDITION WILL CAUSE A WOBBLE OR SHIMMY TO BE FELT IN THE STEERING WHEEL %XCESSIVE DYNAMIC IMBALANCE OF THIS TYPE CREATES A SHIMMY THAT TRANSFERS THROUGH THE SUSPENSION COMPONENTS TO THE OCCUPANTS OF THE VEHICLE ESPECIALLY AT HIGHER SPEEDS $YNAMIC BALANCERS SPIN THE WHEEL IN ORDER TO MEASURE BOTH THE UP AND DOWN IMBALANCE FORCE AND THE WOBBLE OR SHIMMY RELATED IMBALANCE SIDE TO SIDE $YNAMIC BALANCERS DIRECT THE OPERATOR TO PLACE CORRECTION WEIGHTS ON THE INSIDE AND OUTSIDE CORRECTION LOCATIONS OF THE RIM SO THAT BOTH IMBALANCE FORCE AND IMBALANCE WOBBLE WILL BE ELIMINATED
6EHICLE 3PEED 6IBRATIONS -ECHANICAL 5NLOADED 2UNOUT 2UNOUT OF A TIRE AND WHEEL ASSEMBLY DIRECTLY AFFECTS THE AMOUNT OF IMBALANCE AND RADIAL FORCE VARIATION AND SHOULD BE CORRECTED lRST 4HE SMALLER THE AMOUNT OF RUNOUT THE LESS IMBALANCE AND FORCE VARIATION 2ADIAL AND LATERAL RUNOUT CAN BE CORRECTED AT THE SAME TIME 4HERE ARE TWO METHODS TO MEASURE RUNOUT OF THE TIRE AND WHEEL ASSEMBLY s /N VEHICLE s /FF VEHICLE 0RIOR TO PERFORMING A RUNOUT MEASUREMENT ENSURE THAT THE BEADS ARE SEATED EQUALLY AROUND THE CIRCUMFERENCE OF THE TIRE /N VEHICLE MEASUREMENTS REQUIRE THE WHEEL TO BE MOUNTED ONTO THE HUB AND THAT THE WHEEL BEARING IS IN GOOD CONDITION /NCE THE ON VEHICLE RUNOUT HAS BEEN CHECKED THEN ON OFF VEHICLE CHECK SHOULD BE TAKEN )F THERE IS A LARGE DIFFERENCE BETWEEN RUNOUT MEASUREMENTS ON THE VEHICLE AND OFF THE VEHICLE THEN RUNOUT IS DUE TO ONE OF THE FOLLOWING s 3TUD CIRCLE RUNOUT s (UB mANGE RUNOUT s 3OME OTHER MOUNTING CONDITION BETWEEN THE WHEEL AND THE VEHICLE 7HEN DIAGNOSING A TIRE AND WHEEL CONCERN ON A VEHICLE CONSULT THE SERVICE INFORMATION FOR CORRECT SPECIlCATIONS
6EHICLE 3PEED 6IBRATIONS -ECHANICAL 5NLOADED 2ADIAL 2UNOUT
-ECHANICAL 5NLOADED ,ATERAL 2UNOUT
2ADIAL RUNOUT OF THE TIRE AND WHEEL ASSEMBLY SHOULD BE STARTED AT THE TIRE WHILE MOUNTED TO THE VEHICLE )F THE TIRE RADIAL RUNOUT MEASUREMENTS ARE WITHIN SPECIlCATIONS NO FURTHER RADIAL MEASUREMENTS OF THE ASSEMBLY NEED TO BE MEASURED
,ATERAL RUNOUT OF THE TIRE AND WHEEL ASSEMBLY SHOULD BE STARTED AT THE TIRE WHILE MOUNTED TO THE VEHICLE )F THE TIRE LATERAL RUNOUT MEASUREMENTS ARE WITHIN SPECIlCATIONS NO FURTHER LATERAL MEASUREMENTS OF THE ASSEMBLY ARE NEEDED
)F THE RADIAL RUNOUT MEASUREMENTS EXCEED SPECIlCATIONS WHILE MOUNTED ON THE VEHICLE PERFORM THE MEASUREMENTS OFF VEHICLE 4HE TIRE AND WHEEL ASSEMBLY RADIAL RUNOUT CAN BE MEASURED OFF VEHICLE WHEN MOUNTED ON A BALANCING MACHINE
)F THE LATERAL RUNOUT MEASUREMENTS EXCEED SPECIlCATIONS WHILE MOUNTED ON THE VEHICLE PERFORM MEASUREMENTS OFF VEHICLE 4HE TIRE AND WHEEL ASSEMBLY LATERAL RUNOUT CAN BE MEASURED OFF VEHICLE WHEN MOUNTED ON A BALANCING MACHINE
)F THE OFF VEHICLE RUNOUT EXCEEDS SPECIlCATIONS RADIAL RUNOUT OF THE STUD CIRCLE AND HUB mANGE NEEDS TO BE MEASURED 4HE WHEEL TO HUB MOUNTING SHOULD BE CHECKED TO ENSURE THERE ARE NO FAULTS CAUSING THE RUNOUT
)F THE OFF VEHICLE RUNOUT EXCEEDS SPECIlCATIONS LATERAL RUNOUT OF THE STUD CIRCLE AND HUB mANGE NEEDS TO BE MEASURED 4HE WHEEL TO HUB MOUNTING SHOULD BE CHECKED TO ENSURE THERE ARE NO FAULTS CAUSING THE RUNOUT
)F THE OFF VEHICLE MEASUREMENT EXCEEDS SPECIlCATIONS THE RADIAL RUNOUT OF THE WHEEL ASSEMBLY SHOULD BE TAKEN )F THE WHEEL ASSEMBLY EXCEEDS SPECIlCATIONS IT WILL NEED TO BE REPLACED )F THE WHEEL ASSEMBLY MEETS SPECIlCATIONS THE TIRE IS AT FAULT AND WILL NEED TO BE REPLACED
)F THE OFF VEHICLE MEASUREMENT EXCEEDS SPECIlCATIONS THE LATERAL RUNOUT OF THE WHEEL ASSEMBLY SHOULD BE TAKEN )F THE WHEEL ASSEMBLY EXCEEDS SPECIlCATIONS IT WILL NEED TO BE REPLACED )F THE WHEEL ASSEMBLY MEETS SPECIlCATIONS THE TIRE IS AT FAULT AND WILL NEED TO BE REPLACED
6EHICLE 3PEED 6IBRATIONS 2ADIAL &ORCE 6ARIATION 2&6 4HE 2&6 IS AN INDUSTRIAL MEASUREMENT TERM DESCRIBING THE TIRE UNIFORMITY UNDER LOAD MEASURING THE VARIATION UP AND DOWN OF THE LOAD ACTING ON THE VEHICLE SPINDLE !LL TIRES HAVE SOME NON UNIFORMITY IN THE SIDEWALL ANDOR FOOTPRINT DUE TO VARIABLES IN THE MANUFACTURING PROCESS 4IRE UNIFORMITY MEASUREMENT VALUES CAN BE AFFECTED BY RIM WIDTH RIM CONDITION AND MANY DIVERSE TIRE MOUNTING VARIABLES 5NLIKE BALANCING THERE IS OFTEN A SMALL AMOUNT OF 2&6 REMAINING IN THE TIRE AND WHEEL ASSEMBLY AFTER ASSEMBLY AND THIS IS GENERALLY ACCEPTABLE 4O UNDERSTAND THE EFFECTS OF RADIAL FORCE VARIATION ON VIBRATION A MODEL OF A TIRE CAN BE USED 4HE SIDEWALL AND FOOTPRINT CAN BE UNDERSTOOD AS A COLLECTION OF SPRINGS BETWEEN THE RIM AND THE TIRE CONTACT PATCH )F THE hSPRINGSv ARE NOT OF UNIFORM STIFFNESS A VARIED FORCE IS EXERTED ON THE AXLE AND CAUSES IT TO MOVE UP AND DOWN AS THE TIRE ROTATES AND mEXES 4HIS MOVEMENT CREATES A VIBRATION IN THE VEHICLE UNRELATED TO BALANCE ! TIRE WITH NOTICEABLE 2&6 WILL PRODUCE A VIBRATION EVEN THOUGH IT IS PERFECTLY BALANCED AND IS WITHIN THE RADIAL AND LATERAL RUNOUT LIMITS -ANUFACTURERS ATTEMPT TO MINIMIZE THE 2&6 DURING TIRE AND WHEEL ASSEMBLY
4HE 2&6 CAN BE MEASURED BY A LOAD ROLLER PRESSING AGAINST A ROTATING TIRE AND WHEEL ASSEMBLY TO EVALUATE THE MAGNITUDE OF EXISTING ASSEMBLY HARMONICS 4HE (UNTER '30 3ERIES 6IBRATION #ONTROL 3YSTEM IS ONE METHOD OF DETERMINING AND POSSIBLY CORRECTING FOR 2&6 0AINT MARKS OR TAPE STRIPS ON THE TIRE AND WHEEL OR VALVE STEM LOCATION IN THE WHEEL VARY IN PURPOSE -ANUFACTURERS USE THESE MARKINGS FOR HEAVY SPOT 2&6 RUNOUT INVENTORY CONTROL AND SIMILAR PURPOSES 7ITHOUT SPECIlC MANUFACTURER INFORMATION THEY ARE OF LITTLE USE TO THE TECHNICIAN
6EHICLE 3PEED 6IBRATIONS .ATURAL &REQUENCY AND 6IBRATION 4RANSFER #HARACTERISTICS
4READ 0ATTERNS
4IRE NOISE ASSOCIATED WITH TREAD PATTERNS HAS 7HEN A TIRE IS SUBJECTED TO A COMPELLING FORCE TWO CAUSES AT ONE POINT IT ONLY VIBRATES THERE AS LONG AS THE FREQUENCY OF THE COMPELLING FORCE IS LOW s 2EPEATED DEFORMATION OF THE TREAD BELOW (Z 7HEN THE FREQUENCY IS HIGH THE PATTERN GROOVES THAT OCCURS AS THE TIRE WHOLE TIRE STARTS TO VIBRATE 3IMILAR VIBRATIONS ARE ROLLS ON THE ROAD COMBINED WITH THE CAUSED WHEN TIRES ARE EXCITED BY ROAD SURFACE RESULTANT mOW OF AIR IN THE GROOVES IRREGULARITIES 4HESE VIBRATIONS HAVE A LARGE EFFECT s #ONTINUOUS STRIKING OF THE TREAD PATTERN ON UNWANTED HARSHNESS AND ROAD NOISE AGAINST THE ROAD SURFACE 4HE RELATIONSHIP BETWEEN VIBRATION TRANSMISSIBILITY AND EXCITATION FREQUENCY IS CALLED THE hVIBRATION TRANSFER CHARACTERISTICv ! SMOOTH TREAD HAVING NO PATTERN ON THE SURFACE 4HIS IS A MEASURE OF A TIRES OVERALL VIBRATION IS THE MOST SILENT 4HE NOISE LEVELS OF THE TIRE CHARACTERISTIC 2ADIAL AND BIAS TIRES HAVE A TREAD INCREASES IN THE ORDER OF NATURAL FREQUENCY BETWEEN AND (Z RESPECTIVELY 4HE POOR HARSHNESS CHARACTERISTICS 3TRAIGHT RIB WITH GROOVES RUNNING AROUND THE CIRCUMFERENCE OF A RADIAL TIRE ARE DUE TO HIGH TRANSMISSION OF VIBRATIONS AT LOW NATURAL FREQUENCIES OF ABOUT 'ENERAL PURPOSE RIB WITH THE ZIGZAG GROOVES (Z /N THE OTHER HAND THE POOR ROAD NOISE CHARACTERISTICS OF A BIAS TIRE ARE DUE TO HIGH VIBRATION TRANSMISSIBILITY AT NATURAL FREQUENCIES 4IRE NOISE ASSOCIATED WITH TREAD PATTERNS WILL NEAR (Z CHANGE PITCHES WHEN DRIVEN ON DIFFERENT ROAD 4IRE AND WHEEL .6( CONCERNS ARE LOW FREQUENCY SURFACES $IAGNOSING TIRE NOISE IS ACCOMPLISHED BY DRIVING THE VEHICLE ON DIFFERENT TYPES OF ROAD USUALLY AROUND TO (Z +NOWING THE SURFACES IE ASPHALT AND CONCRETE 4HE TIRE NATURAL FREQUENCY AND VIBRATION TRANSFER NOISE WILL STILL BE PRESENT HOWEVER IT WILL SOUND CHARACTERISTICS OF DIFFERENT TIRES CAN HELP DIFFERENT ON THE DIFFERENT ROAD SURFACES 3IMILAR DETERMINE IF AN .6( CONCERN IS DUE TO THE TIRE VEHICLES WITH THE SAME TYPE TIRES WILL ALSO TYPE OR IF THE TIRE IS IN NEED OF SERVICE BECAUSE EXHIBIT THE SAME NOISE CHARACTERISTICS OF A RUNOUT OR IMBALANCE CONDITION
6EHICLE 3PEED 6IBRATIONS 4IRE 6IBRATION &ORMULAS 4O DETERMINE IF A VEHICLE SPEED RELATED VIBRATION IS BEING CAUSED BY A TIRE AND WHEEL ASSEMBLY USE THE TIRE VIBRATION FORMULAS 4IRE AND WHEEL CALCULATIONS ARE PERFORMED IN MPH KPH INCREMENTS "EGIN BY CALCULATING THE NUMBER OF TIRE AND WHEEL ROTATIONS IN MPH KPH INCREMENTS 4HE NEXT STEP IS TO CALCULATE THE 203 PER EVERY MPH KPH 4HEN CALCULATE THE VEHICLE SPEED WHERE THE VIBRATION OCCURS IN MPH KPH INCREMENTS AND CALCULATE THE TIRE AND WHEEL ASSEMBLY (Z RATE AT THE VIBRATION SPEED 4IRE 2EVOLUTIONS PER MPH KPH &ORMULA 5SE THE FOLLOWING FORMULA TO DETERMINE THE 203 PER MPH KPH
! N S W E R A B O V E 7 H E E L D I A M E T E R v M M 4 I RE D I A M E T E R $ETERMINE 203 IN MPH KPH INCREMENTS USING THE FOLLOWING FORMULA
$IVIDE BY THE TIRE DIAMETER
-ULTIPLY THE ABOVE ANSWER BY
$IVIDE THE ABOVE ANSWER BY
6ERIFY THE TIRE SIZE ON THE VEHICLE $ETERMINE TIRE DIAMETER BY USING THE FOLLOWING FORMULA
-ULTIPLY THE TIRE ASPECT RATIO BY THE TIRE WIDTH
$IVIDE THE ABOVE ANSWER BY
-ULTIPLY THE ABOVE ANSWER BY
!DD THE ABOVE ANSWER TO THE WHEEL DIAMETER
%XAMPLE 02 ! S P E C T R A T I O X 4 I RE W I D T H X
%XAMPLE 02 4 I RE D I A M E T E R !NSWER ABOVE X X !NSWER ABOVE 2 0 3 A T M P H K P H 4HIS FORMULA HAS DETERMINED THAT A 02 TIRE REVOLVES TIMES PER SECOND FOR EVERY MPH KPH INCREMENT 5SING THE 203 PER MPH KPH THE (Z RATE OF THE TIRE AND WHEEL ASSEMBLY AT A GIVEN VEHICLE SPEED CAN NOW BE DETERMINED 5SE THE 4IRE AND 7HEEL (: &ORMULA TO CALCULATE THE (Z RATE AT A GIVEN VEHICLE SPEED
!NSWER ABOVE !NSWER ABOVE X X
6EHICLE 3PEED 6IBRATIONS 4IRE AND WHEEL (Z &ORMULA 5SE THE TIRE AND WHEEL (Z FORMULA TO CALCULATE A -ULTIPLY THE VEHICLE MPH KPH INCREMENT TIRE AND WHEEL (Z RATE AT A GIVEN VEHICLE SPEED BY THE TIRE AND WHEEL 203 PER MPH KPH 2EMEMBER ALL TIRE AND WHEEL CALCULATIONS ARE DETERMINED IN MPH KPH INCREMENTS
"EGIN TO CALCULATE TIRE AND WHEEL FREQUENCY IN MPH KPH INCREMENTS BY PERFORMING THE FOLLOWING STEPS $IVIDE VEHICLE SPEED MPH BY KPH BY
4HIS STEP IS NECESSARY DUE TO ALL CALCULATIONS BEING DONE IN MPH KPH INCREMENTS 6E H I C L E S P E E D M P H I N C RE M E N T
&OR EXAMPLE IF THE CORRESPONDING SPEED OF AN .6( PROBLEM ON A VEHICLE IS MPH KPH THE RESULTING MPH KPH INCREMENT IS NINE M P H I N C RE M E N T S
5SE THE 4IRE 2EVOLUTIONS AT -0( +0( &ORMULA PREVIOUS PAGE TO DETERMINE THE TIRE AND WHEEL 203 PER MPH KPH
%XAMPLE FROM PREVIOUS PAGE )F THE TIRE SIZE ON THE VEHICLE IS 02 THEN THE 203 PER MPH KPH IS
4HIS DETERMINES HOW MANY TIMES THE TIRE AND WHEEL ASSEMBLY REVOLVES PER SECOND AT THE VEHICLE SPEED WHERE THE VIBRATION OCCURS
M P H I N C RE M E N T X 4 I RE 2 0 3 M P H TI RE A N D W H E E L 20 3 A T V I B RA T I O N SP EED
%XAMPLE 02 AT MPH X 2 0 3 A T M P H
4HE TIRE AND WHEEL ASSEMBLY REVOLVES TIMES PER SECOND OR (Z AT THE VEHICLE SPEED OF MPH KPH 4HE CALCULATED FREQUENCY OF (Z IS THE lRST ORDER TIRE AND WHEEL FREQUENCY 4HE SECOND ORDER FREQUENCY OF THE TIRE AND WHEEL ASSEMBLIES IS TWICE THIS NUMBER OR (Z X ( Z 4HE THIRD ORDER FREQUENCY IS THREE TIMES THIS NUMBER OR (Z X ( Z
6EHICLE 3PEED 6IBRATIONS $RIVE 3HAFT &REQUENCY &ORMULA +NOWING THE TIRE AND WHEEL FREQUENCY ALLOWS FOR EASY CALCULATION OF DRIVE SHAFT FREQUENCY 4HE DRIVE SHAFT DRIVES THE TIRES THROUGH THE REAR AXLE 4HEREFORE TO DETERMINE DRIVE SHAFT FREQUENCY MULTIPLY TIRE AND WHEEL FREQUENCY BY THE RATIO OF THE RING AND PINION #ALCULATE DRIVE SHAFT FREQUENCY BY PERFORMING THE FOLLOWING STEPS
4HIS RESULTS IN A DRIVE SHAFT FREQUENCY OF (Z AT THE VEHICLE SPEED OF MPH KPH 4HE CALCULATED FREQUENCY OF (Z IS THE lRST ORDER DRIVE SHAFT FREQUENCY 4HE SECOND ORDER FREQUENCY OF THE DRIVE SHAFT IS TWICE THIS NUMBER OR (Z
/BTAIN THE AXLE RATIO X
-ULTIPLY THE TIRE AND WHEEL FREQUENCY AT VIBRATION SPEED BY THE AXLE RATIO 4 I RE ( Z X ! X L E R A T I O $ RI V E S H A FT F RE Q U E N C Y &OR EXAMPLE A 02 EQUIPPED VEHICLE WITH A VIBRATION AT MPH KPH AND AN AXLE RATIO OF 5SING THIS INFORMATION MULTIPLY (Z THE TIRE AND WHEEL FREQUENCY AT MPH CALCULATED BY USING THE 4IRE AND 7HEEL &REQUENCY &ORMULA BY THE AXLE RATIO OF X ( Z
)T IS IMPORTANT TO REMEMBER THE DIFFERENCE BETWEEN DRIVE SHAFT AND AXLE SHAFT FREQUENCIES 4HE FREQUENCY OF DRIVE SHAFT CONCERNS ARE HIGH SINCE THEY ROTATE APPROXIMATELY THREE TO FOUR TIMES THAT OF THE TIRE AND WHEEL ASSEMBLIES !XLE SHAFT CONCERNS ARE LOWER FREQUENCY BECAUSE THEY ROTATE AT TIRE AND WHEEL SPEED
6EHICLE 3PEED 6IBRATIONS $RIVE 3HAFTS
$RIVELINE 6IBRATION
4HE FUNCTION OF A DRIVE SHAFT IS TO TRANSMIT POWER $RIVELINE VIBRATIONS CAN BE CAUSED BY FROM ONE POINT TO ANOTHER IN A SMOOTH ACTION s $AMAGED DRIVE SHAFTS 4HE SHAFTS ARE DESIGNED TO SEND TORQUE THROUGH s -ISSING SHAFT BALANCE WEIGHTS AN ANGLE FROM THE TRANSMISSION TRANSFER CASE ON !7$ VEHICLES TO THE AXLE s 7ORN OR OUT OF BALANCE WHEELS 5SE EXACT REPLACEMENT PARTS FOR ATTACHING THE DRIVE SHAFTS 4HIS ENSURES SAFE OPERATION 4HE SPECIlED TORQUE ALWAYS MUST BE APPLIED WHEN TIGHTENING THE FASTENERS /FTEN !UDI VEHICLES WILL HAVE SPECIAL PROCEDURES TO ALIGN THE ENGINE AND TRANSMISSION IN THE VEHICLE 4HERE ARE SPECIAL PROCEDURES TO ALIGN THE DRIVE SHAFTS AS WELL $RIVE SHAFT VIBRATIONS CAN BE CLASSIlED INTO THREE DIFFERENT ORDERS lRST ORDER SECOND ORDER AND FOURTH ORDER ! lRST ORDER VIBRATION MAY BE CAUSED BY A BENT OR OUT OF BALANCE DRIVE SHAFT CONDITION ! SECOND ORDER VIBRATION MAY BE CAUSED BY DRIVE SHAFT ANGLE 5 JOINT CANCELLATION AND WORN #6 JOINTS OR 5 JOINTS ! FOURTH ORDER VIBRATION MAY BE CAUSED BY A WORN #6 JOINT OR 5 JOINT
s ,OOSE WHEEL BOLTS s 7ORN 5 JOINTS OR CONSTANT VELOCITY JOINTS s ,OOSE OR BROKEN SPRINGS s ,OOSE PINION GEAR NUT s %XCESSIVE PINION YOKE RUNOUT )N ADDITION CHECK FOR LOOSE OR DAMAGED FRONT END COMPONENTS OR ENGINETRANSMISSION MOUNTS 4HESE COMPONENTS CAN CONTRIBUTE TO WHAT APPEARS TO BE A REAR END VIBRATION $O NOT OVERLOOK ENGINE ACCESSORIES BRACKETS AND DRIVE BELTS !LL DRIVELINE COMPONENTS SHOULD BE EXAMINED BEFORE ATTEMPTING ANY REPAIR
6EHICLE 3PEED 6IBRATIONS "ENT $RIVE 3HAFTS ! BENT DRIVE SHAFT CAN CAUSE A VIBRATION IN THE VEHICLE )F A BENT DRIVE SHAFT IS SUSPECTED PERFORM A RUNOUT CHECK ON THE DRIVE SHAFT 4HE DIAL INDICATOR MUST BE PLACED AT A DEGREE ANGLE FROM THE DRIVE SHAFT FOR ACCURATE READINGS &IRST MEASURE THE RUNOUT CLOSE TO EACH YOKE WELD AND VERIFY IT IS WITHIN THE SPECIlCATIONS IN THE SERVICE INFORMATION 4HE SECOND MEASUREMENT IS DONE IN THE CENTER OF THE DRIVE SHAFT TO VERIFY IT IS WITHIN SPECIlCATIONS )F THE RUNOUT IS NOT WITHIN THE SPECIlCATIONS THE DRIVE SHAFT MUST BE REPLACED &RONT $RIVE 3HAFTS
2EAR $RIVE 3HAFTS
6EHICLE 3PEED 6IBRATIONS 4RANSMISSION .OISE AND 6IBRATIONS 4RANSMISSION RELATED CONCERNS CAN CAUSE NOISE OR VIBRATIONS 4HE PURPOSE OF THE TRANSMISSION IS TO PROVIDE SEVERAL DIFFERENT GEAR RANGES TO IMPROVE VEHICLE TORQUE AND ACCELERATION QUALITIES 4HE DIFFERENT GEAR RANGES ROTATE AT DIFFERENT SPEEDS FROM THE TIRE AND WHEEL AND SHAFTS )F THE TRANSMISSION IS CAUSING THE NOISE AND VIBRATION IT WILL USUALLY CHANGE CHARACTERISTICS WHEN THE DIFFERENT GEAR RANGES ARE SELECTED -OST TRANSMISSION NOISES AND VIBRATION WILL NOT BE PRESENT WHEN THE TRANSMISSION IS PLACED IN NEUTRAL DURING THE ROAD TEST -ANUAL TRANSMISSIONS UTILIZE A CLUTCH ASSEMBLY BETWEEN THE ENGINE AND TRANSMISSION 4HE CLUTCH ASSEMBLY CAN CAUSE NOISE AND VIBRATION )F IT IS SUSPECTED THAT THE MANUAL TRANSMISSION IS CAUSING NOISE AND VIBRATION REFER TO THE TRANSMISSION SECTION OF THE SERVICE INFORMATION FOR DIAGNOSTIC PROCEDURES !UTOMATIC TRANSMISSIONS UTILIZE A TORQUE CONVERTER BETWEEN THE ENGINE AND TRANSMISSION 4HE TORQUE CONVERTER IS DRIVEN AT ENGINE SPEED 4ORQUE CONVERTER FREQUENCY WILL MATCH ENGINE FREQUENCY ! LOCKING TORQUE CONVERTER IMPROVES FUEL MILEAGE AND REDUCES ENGINE EMISSIONS 4HIS COMPONENT CAN CAUSE NOISE AND VIBRATION CONCERNS 4HE TORQUE CONVERTER OPERATION CAN BE MONITORED WITH A SCAN TOOL 2EFER TO SERVICE INFORMATION TO DIAGNOSE TORQUE CONVERTER CONCERNS
6EHICLE 3PEED 6IBRATIONS $IFFERENTIAL /PERATION 4HE DIFFERENTIAL GEAR SYSTEM DIVIDES THE TORQUE BETWEEN THE AXLE SHAFTS )T ALLOWS THE AXLE SHAFTS TO ROTATE AT DIFFERENT SPEEDS WHEN TURNING CORNERS -OST DIFFERENTIALS CONSIST OF A PAIR OF SIDE GEARS AND A PAIR OF PINION GEARS %ACH DIFFERENTIAL SIDE GEAR IS SPLINED TO AN OUTPUT SHAFT 4HE PINION GEARS ARE MOUNTED ON A PINION SHAFT AND ARE FREE TO ROTATE ON THE SHAFT 4HE PINION GEAR IS lTTED IN A BORE IN THE DIFFERENTIAL CASE AND IS POSITIONED AT A RIGHT ANGLE TO THE AXLE SHAFTS )N OPERATION POWER mOW OCCURS AS FOLLOWS s 4HE PINION GEAR ROTATES THE RING GEAR s 4HE RING GEAR BOLTED TO THE DIFFERENTIAL CASE ROTATES THE CASE s )N STRAIGHT AHEAD DRIVING THE DIFFERENTIAL CASE ROTATES AS ONE COMPLETE UNIT NO DIFFERENTIAL GEARS PINION OR SIDE GEARS ROTATE AND TRANSMIT POWER TO THE OUTPUT SHAFTS s 7HEN CORNERING THE DIFFERENTIAL PINION GEARS MOUNTED ON THE PINION SHAFT IN THE CASE ROTATE THE SIDE GEARS AT A DIFFERENCE IN SPEED ALLOWING THE TIRES TO ROTATE SMOOTHLY s 4HE SIDE GEARS SPLINED TO THE OUTPUT SHAFTS ROTATE THE SHAFTS DURING STRAIGHT AHEAD DRIVING OR CORNERING
3TRAIGHT !HEAD $RIVING $URING STRAIGHT AHEAD DRIVING THE DIFFERENTIAL PINION GEARS DO NOT ROTATE ON THE DIFFERENTIAL PINION SHAFT BECAUSE INPUT TORQUE APPLIED TO THE GEARS IS DIVIDED AND DISTRIBUTED EQUALLY BETWEEN THE TWO SIDE GEARS !S A RESULT THE PINION GEARS REVOLVE WITH THE DIFFERENTIAL PINION SHAFT BUT DO NOT ROTATE AROUND IT 4URNING #ORNERS 4HE OUTSIDE WHEEL MUST TRAVEL A GREATER DISTANCE THAN THE INSIDE WHEEL IN ORDER TO COMPLETE A TURN 4HE DIFFERENCE MUST BE COMPENSATED FOR TO PREVENT THE TIRES FROM SCUFlNG AND SKIDDING THROUGH TURNS 4HE DIFFERENTIAL ALLOWS THE AXLE SHAFTS TO TURN AT UNEQUAL SPEEDS )N THIS INSTANCE THE INPUT TORQUE APPLIED TO THE PINION GEARS IS NOT DIVIDED EQUALLY 4HE PINION GEARS NOW ROTATE AROUND THE PINION MATE SHAFT IN OPPOSITE DIRECTIONS 4HIS ALLOWS THE SIDE GEAR AND AXLE SHAFT ATTACHED TO THE OUTSIDE WHEEL TO ROTATE AT A FASTER SPEED )F A NOISE OR VIBRATION IS BEING CAUSED BY THE DIFFERENTIAL THE CONCERN WILL USUALLY CHANGE CHARACTERISTICS DURING STRAIGHT AHEAD DRIVING AND WHEN TURNING CORNERS 4HIS IS DUE TO THE DIFFERENT OPERATION OF THE DIFFERENTIAL WHEN TURNING $IFFERENTIAL NOISES ARE OFTEN TORQUE SENSITIVE RESULTING IN CHARACTERISTIC CHANGES WHEN CHANGING TORQUE INPUT $URING A ROAD TEST DRIVE IN A lGURE PATTERN IN A SAFE AND OPEN AREA AND DETERMINE IF THE .6( CONCERN IS MORE PRONOUNCED WHILE LOADING THE DIFFERENTIAL GEARS #ONSULT THE AXLE SECTION OF SERVICE INFORMATION IF IT IS SUSPECTED THE DIFFERENTIAL IS CAUSING A NOISE OR VIBRATION CONCERN
6EHICLE 3PEED 6IBRATIONS "EARING .OISE
'EAR .OISE
7HEEL BEARINGS AND PINION AND DIFFERENTIAL GEAR BEARINGS CAN PRODUCE NOISE WHEN WORN OR DAMAGED "EARING NOISE CAN BE EITHER A WHINING OR A GROWLING SOUND
'EAR NOISE USUALLY OCCURS AT SPECIlC SPEED RANGES USUALLY BETWEEN AND MPH AND KPH OR ABOVE MPH KPH 'EAR NOISE CAN ALSO OCCUR DURING SPECIlC DRIVING CONDITIONS SUCH AS ACCELERATION DECELERATION COAST OR CONSTANT LOAD 'EAR NOISES USUALLY DISAPPEAR IF THE VEHICLE IS ALLOWED TO COAST WITHOUT ANY ACCELERATION OR DECELERATION TORQUE APPLIED TO THE GEARS
&AULTY WHEEL BEARINGS PRODUCE NOISE THAT GENERALLY CHANGES WHEN THE BEARINGS ARE LOADED 7HEN ROAD TESTING THE VEHICLE TURN THE VEHICLE SHARPLY TO THE LEFT AND RIGHT 4HIS LOADS THE BEARINGS AND CHANGES THE NOISE LEVEL 7HEN WHEEL BEARING DAMAGE IS SLIGHT THE NOISE IS USUALLY NOT NOTICEABLE AT SPEEDS ABOVE MPH KPH
$RIVELINE 3NAP
0INION BEARINGS USUALLY CHANGE NOISE CHARACTERISTICS WHEN TORQUE INPUT IS CHANGED IE ! SNAP OR CLUNK NOISE WHEN THE VEHICLE IS SHIFTED INTO GEAR OR THE CLUTCH IS ENGAGED CAN COASTING OR HARD ACCELERATIONS BE CAUSED BY s (IGH ENGINE IDLE SPEED s ,OOSE ENGINETRANSMISSIONTRANSFER CASE MOUNTS 7HEEL "EARING
s 7ORN 5 JOINTS s ,OOSE AXLE MOUNTS s ,OOSE PINION GEAR NUT AND YOKE s %XCESSIVE RING GEAR BACKLASH s %XCESSIVE SIDE GEARCASE CLEARANCE
!XLE 3HAFT 7HEEL (UB
4HE SOURCE OF A SNAP OR CLUNKING NOISE CAN BE DETERMINED BY RAISING THE VEHICLE ON A HOIST WITH THE WHEELS FREE TO ROTATE (AVE ANOTHER TECHNICIAN SHIFT THE TRANSMISSION INTO GEAR AND LISTEN FOR THE NOISE ! STETHOSCOPE EITHER MANUAL OR ELECTRONIC IS HELPFUL IN ISOLATING THE SOURCE OF THE NOISE 5SE CAUTION WHEN WORKING AROUND ROTATING COMPONENTS
6EHICLE 3PEED 6IBRATIONS 3USPENSION #OMPONENTS 4HE SUSPENSION SYSTEM PLAYS A LARGE ROLE IN THE EFFECTS OF .6( ON A VEHICLE 3IMILAR TO THE STEERING SYSTEM COMPONENTS THE SUSPENSION OF A VEHICLE CAN EASILY ACT AS THE MEDIUM THROUGH WHICH VIBRATION CAN BE TRANSFERRED 7HEN THE SOURCE OF AN .6( CONCERN IS DETERMINED YOU USUALLY CAN lND THE CAUSE BY PERFORMING A THOROUGH VISUAL INSPECTION 0ASSENGERS OF A VEHICLE ARE SENSITIVE TO THE EFFECTS OF A HARSH RIDING SUSPENSION &OR THIS REASON VARIOUS MEASURES ARE TAKEN IN THE DESIGN AND DEVELOPMENT PHASE OF A VEHICLES SUSPENSION &OR EXAMPLE SPRINGS AND BUSHINGS ARE CAREFULLY SELECTED TO PROVIDE A SMOOTH RIDE AND ALSO TO REDUCE THE IMPACT OF STEERING FORCES 4HE VIBRATION OF A VEHICLES SUSPENSION SYSTEM CONSISTS OF VERTICAL AND LONGITUDINAL FORCES 4HE VERTICAL FORCES ARE CONTROLLED BY WELL PROPORTIONED SPRUNG AND UNSPRUNG WEIGHTS SHOCKS AND COIL SPRINGS
"USHINGS ARE DESIGNED SO THEY ARE SOFTER IN ONE AREA THAN IN ANOTHER "USHINGS ARE MADE SOFTER IN THE LONGITUDINAL DIRECTION SO THE EFFECTS OF TIRE IMPACT OR ROAD SHOCK ARE REDUCED "USHINGS ARE MADE STIFFER IN THE LATERAL DIRECTION SO STEERING THE VEHICLE DOES NOT HAVE AS MUCH OF AN ADVERSE EFFECT )T IS IMPORTANT THAT BUSHINGS AND INSULATORS ARE IN GOOD CONDITION AND THEY ARE OF THE SPECIlED TYPE IN ORDER TO AVOID .6( CONCERNS IN THE SUSPENSION .OISE FROM THE SUSPENSION IS TYPICALLY CAUSED BY ONE OF THE FOLLOWING s ,OOSE COMPONENTS s 7ORN BUSHINGS s 0OOR LUBRICATION
,ONGITUDINAL FORCES ARE CONTROLLED BY CAREFUL SELECTION OF SUSPENSION BUSHINGS 4HE SUSPENSION OF A PARTICULAR VEHICLE IS DESIGNED SO THAT THE LOWER CONTROL ARMS ABSORB LONGITUDINAL IMPACTS FROM THE TIRES 4IRE IMPACT IS FURTHER DAMPENED BY BUSHINGS BEFORE BEING TRANSMITTED THROUGH THE CROSSMEMBER TO THE BODY 4HIS LONGITUDINAL COMPLIANCE DEPENDS ON THE SPRING CONSTANT RATE OF THE RUBBER INSULATOR BUSHINGS
6EHICLE 3PEED 6IBRATIONS 3TEERING #OMPONENTS -ANY CUSTOMER CONCERNS REGARDING .6( ARE RELATED TO THE STEERING SYSTEM 4HIS IS BECAUSE THE DRIVER IS HOLDING THE STEERING WHEEL AT ALL TIMES WHILE DRIVING AND ANY VIBRATIONS FROM THE TIRES OR SUSPENSION ARE TRANSFERRED TO THE STEERING COMPONENTS .OISE RELATED CONCERNS ARE USUALLY GENERATED WITHIN THE STEERING SYSTEM ITSELF 6IBRATION RELATED CONCERNS CAN BE CAUSED BY MANY DIFFERENT COMPONENTS INCLUDING COMPONENTS IN THE SUSPENSION TIRES AND WHEELS .OISE 3OME STEERING SYSTEM SOUNDS ARE NORMAL AND SHOULD NOT BE OF CONCERN 4HERE ARE SOME INHERENT NOISES IN ALL POWER STEERING SYSTEMS (OWEVER OTHER SOUNDS MAY INDICATE A PROBLEM WITHIN THE STEERING SYSTEM -ANY NORMAL STEERING SYSTEM SOUNDS ARE RELATED TO THE POWER STEERING PUMP (ISSING AND RATTLING ARE TWO STEERING SYSTEM RELATED NOISES THAT MAY OCCUR
(ISS ! HISSING NOISE USUALLY ORIGINATES IN THE STEERING GEARBOX AND POWER STEERING PUMP 7ITH THE VEHICLE STATIONARY A HISSING SOUND MAY BE HEARD WHEN THE STEERING WHEEL IS TURNED WHICH RESULTS FROM mUID PRESSURE PULSATION IN THE PUMP 7HEN DIAGNOSING A HISSING NOISE CONCERN lRST INSPECT ALL STEERING HOSES TO ENSURE THEY ARE NOT TOUCHING OTHER PARTS OF THE VEHICLE #HECK SERVICE INFORMATION AND TECHNICAL SERVICE BULLETINS FOR POSSIBLE UPDATED HOSES OR HOSE ROUTINGS WHEN DIAGNOSING A HISSING CONCERN 2ATTLE 2ATTLE USUALLY ORIGINATES IN THE STEERING GEAR 4HE POSSIBLE CAUSES FOR THIS CONDITION ARE s 7ORN STEERING OR SUSPENSION COMPONENTS s 7ORN OR DAMAGED RACK AND PINION RETAINERS AND BUSHINGS s 0RESSURE HOSES TOUCHING OTHER VEHICLE COMPONENTS
4OOLS 3IROMETER 6IBRATACH 4HE SIROMETER IS A TOOL THAT IS USEFUL WHEN DIAGNOSING .6( CONCERNS /RIGINALLY USED FOR READING SMALL ENGINE RPM THIS INEXPENSIVE TOOL IS HIGHLY ACCURATE FOR MEASURING VIBRATION FREQUENCIES 4HE SIROMETER HAS ENOUGH RANGE TO MEASURE THE MAJORITY IF NOT ALL OF AN AUTOMOBILES VIBRATION FREQUENCIES 4HE TOOL CAN BE PURCHASED AT MOST FULL SERVICE SMALL ENGINE REPAIR AND PARTS CENTERS 4HE SIROMETER HAS A WIRE THAT WHEN ADJUSTED TO THE PROPER LENGTH RESONATES TO THE VIBRATION FREQUENCY 4O USE THE SIROMETER HOLD IT AGAINST A VIBRATING COMPONENT 2OTATE THE DIAL TO EXTEND THE WIRE AND CHANGE THE WIRES RESONANT FREQUENCY UNTIL THE WIRE VIBRATES AT ITS WIDEST ARC 4HEN READ THE FREQUENCY ON THE TOOLS FACE LABELED #YCLES 0ER 3ECOND n (ERTZ !LWAYS ADJUST THE LENGTH OF THE WIRE FROM ITS SMALLEST LENGTH TO ITS LONGEST LENGTH TO ENSURE ALL FREQUENCIES ARE BEING RECORDED )T IS POSSIBLE TO HAVE MORE THAN ONE VIBRATION PRESENT IN A VEHICLE
4OOLS %6! ))£ 4HE %6! )) ALLOWS FOR A SYSTEMATIC COLLECTION OF INFORMATION THAT IS NECESSARY TO ACCURATELY DIAGNOSE AND REPAIR .6( PROBLEMS 4HE PROPER USE OF THE %6! )) CAN SIGNIlCANTLY REDUCE VEHICLE SERVICE TIME 4HE TOOL USES AN ELECTRONIC PICK UP THAT MEASURES VIBRATION FREQUENCY AND AMPLITUDE !N ADDITIONAL PICK UP CAN BE ADDED AND TWO SOURCES OF VIBRATIONS CAN BE COMPARED 4HE PICK UPS CAN BE PLACED ANYWHERE ON THE VEHICLE "Y PLACING THE PICK UP ON DIFFERENT AREAS OF THE VEHICLE AND COMPARING THE VIBRATIONS AMPLITUDE AS DISPLAYED ON THE SCREEN THE SOURCE OF THE VIBRATION CAN BE LOCATED BY THE HIGHEST AMPLITUDE )F THE STEERING WHEEL OR PASSENGERS SEAT IS VIBRATING THE PICK UP CAN BE PLACED THERE TO MEASURE THE VIBRATION
4HE %6! )) CONTAINS A SOFTWARE DATABASE THAT CONTAINS MOST TIRE SIZES AND AXLE GEAR RATIOS 7HEN THE CORRECT VEHICLE INFORMATION IS ENTERED INTO THE %6! )) THE TOOL WILL DETERMINE AND DISPLAY THE SOURCES OF THE VIBRATION 4HIS FEATURE ELIMINATES MOST OF THE MATHEMATICAL FORMULAS AND CALCULATES THE KNOWN FREQUENCIES OF ROTATING COMPONENTS 4HE %6! )) CAN RECORD SNAPSHOTS DURING A ROAD TEST AND THE DATA REPLAYED TO DETERMINE THE VIBRATION FREQUENCY 4HIS IS USEFUL FOR INTERMITTENT OR SHORT DURATION VIBRATIONS 4HE %6! )) HAS FEATURE TO USE AN INDUCTIVE PICK UP TIMING LIGHT TO VISUALLY mASH A VIBRATION FREQUENCY 4HE OPERATION MANUAL FOR THE TOOL DESCRIBES HOW TO USE THIS FEATURE TO HELP IN DIAGNOSING THE LOCATION OF A VIBRATIONS SOURCE 4HE mASHING TIMING LIGHT CAN BE USED TO BALANCE PROPELLER SHAFTS #ONTACT %QUIPMENT 3OLUTIONS FOR MORE INFORMATION ON THE %6! ))
4OOLS #HASSIS%!2£ 4HE #HASSIS%!2 IS A VERSATILE ELECTRONIC LISTENING TOOL THAT ALLOWS THE USER TO LISTEN TO AMPLIlED SOUNDS THROUGH A PROFESSIONAL SET OF HEADPHONES 4HE PROPER USE OF THE #HASSIS%!2 CAN REDUCE THE TIME IN DIAGNOSING .6( CONCERNS ON A VEHICLE 4HE TOOL HAS MULTIPLE MICROPHONE INPUTS THAT CAN BE PLACED IN DIFFERENT SECTIONS OF THE VEHICLE !TTACHMENT OF THE SIX MICROPHONES AND CLAMPS HELPS TO LOCATE MANY DIFlCULT TO DIAGNOSE VEHICLE PARTS $URING A ROAD TEST THESE PARTS DO NOT MAKE THE SAME SOUNDS AS WHEN THE CAR IS ON A HOIST 4O ACCURATELY DIAGNOSE AN UNDER VEHICLE PROBLEM OPERATE THE VEHICLE SO ALL PARTS AND BEARINGS ARE UNDER FULL LOAD 4HE DIFFERENT INPUTS ALLOW THE LOUDEST AREA TO BE DETERMINED AND THUS DETERMINE THE POSSIBLE SOURCE 0LACE THE MICROPHONES ON PARTS OR AREAS SUSPECTED AS BEING THE POSSIBLE SOURCE 3OME OF THESE VEHICLE PARTS AND AREAS INCLUDE
2EMEMBER THAT NOISES CAN BE CAUSED FROM A VIBRATION THAT RESONATES THROUGH ANOTHER COMPONENT CAUSING IT TO VIBRATE !LWAYS CHECK FOR A VIBRATION FREQUENCY WHEN BEGINNING TO DIAGNOSE A NOISE CONCERN #ONTACT %QUIPMENT 3OLUTIONS FOR MORE INFORMATION ON THE #HASSIS%!2
s 7HEEL BEARINGS s "RAKE CALIPERS s #6 JOINTS s ,EAF AND COIL SPRINGS s $IFFERENTIAL s 4RANSMISSION s "ODY SQUEAKS AND RATTLES s 5NDER DASH s &UEL INJECTORS s 'ENERATOR s 7ATER PUMP s 3MOG PUMP s 0OWER STEERING PUMP s !IR CONDITIONING COMPRESSORS
4OOLS /THER 4OOLS 3EVERAL AUTOMOTIVE TOOL MANUFACTURERS HAVE DEVELOPED ELECTRONIC TOOLS FOR MEASURING AND RECORDING NOISES AND VIBRATIONS 3OME OF THESE TOOLS HAVE MULTIPLE VIBRATION AND NOISE INPUTS RECORDING AND GRAPHING CAPABILITIES .OT ALL OF THE TOOLS AVAILABLE HAVE BEEN COVERED 0LEASE CONTACT AUTOMOTIVE TOOL MANUFACTURERS TO REQUEST INFORMATION
'LOSSARY .6( 4ERMINOLOGY !UDIBLE 2ANGE OF 3OUND n 3OUNDS THAT ARE IN THE RANGE OF TO (ERTZ (Z
&REQUENCY n 4HE NUMBER OF COMPLETE CYCLES THAT OCCURS IN A GIVEN PERIOD OF TIME
!MPLITUDE n 4HE VERTICAL MEASUREMENT BETWEEN THE TOP AND BOTTOM OF A WAVE !LSO SEE MAGNITUDE
(ARSHNESS n !N AGGRESSIVE SUSPENSION FEEL OR LACK OF GIVE IN RESPONSE TO A SINGLE INPUT
"EAT n !N .6( CONCERN PRODUCED BY TWO SOUNDS THAT IS MOST NOTICEABLE WHEN THE FREQUENCY DIFFERENCE IS TO (Z "EAD 3EATING n 4HE PROCESS OF SEATING THE TIRE TO THE RIM )F PROPERLY LUBRICATED THE BEAD SEATING OCCURS WHEN THE TIRE AND WHEEL ARE ASSEMBLED #OMPELLING &ORCE n ! VIBRATING OBJECT ACTING UPON ANOTHER OBJECT THAT CAUSES THE OTHER OBJECT TO VIBRATE
(ERTZ n 4HE UNIT OF FREQUENCY MEASUREMENT IN SECONDS A VIBRATION OCCURRING TIMES PER SECOND WOULD BE AN (Z VIBRATION )NTENSITY n 4HE PHYSICAL QUALITY OF SOUND THAT RELATES TO THE AMOUNT AND DIRECTION OF THE mOW OF ACOUSTIC ENERGY AT A GIVEN SPEED ,ATERAL 2UNOUT n ! CONDITION WHERE A ROTATING COMPONENT DOES NOT ROTATE IN A TRUE PLANE 4HE COMPONENT MOVES SIDE TO SIDE WOBBLES ON ITS ROTATIONAL AXIS
-AGNITUDE !MPLITUDE n 4HE AMOUNT OF FORCE #YCLE n 4HE PATH A WAVE TRAVELS BEFORE THE WAVE OR THE INTENSITY OF THE VIBRATION 4HE MAGNITUDE BEGINS TO REPEAT THE PATH AGAIN OR STRENGTH OF A VIBRATION IS ALWAYS GREATEST AT THE POINT OF RESONANCE $AMPEN n 4O REDUCE THE MAGNITUDE OF A NOISE OR VIBRATION $AMPERS n ! COMPONENT USED TO DAMPEN A NOISE OR VIBRATION &OAM AND RUBBER ARE COMMONLY USED TO DAMPEN VIBRATIONS
-EDIUM n 0ROVIDES A PATH FOR SOUND WAVES TO TRAVEL THROUGH
.ATURAL &REQUENCY n 4HE FREQUENCY THAT A COMPONENT WILL VIBRATE THE EASIEST .ORMALLY $YNAMIC "ALANCE n ! PROCEDURE THAT BALANCES A THE LARGER THE MASS THE LOWER ITS NATURAL TIRE AND WHEEL ASSEMBLY IN TWO PLANES $YNAMIC FREQUENCY BALANCE REMOVES RADIAL AND LATERAL VIBRATIONS s %NGINE BLOCK (Z s 4IRE AND WHEEL ASSEMBLIES (Z n $RONING (IGH 3PEED n ! LONG DURATION NON PROPORTIONAL TO VEHICLE SPEED DIRECTIONAL HUMMING NOISE THAT IS UNCOMFORTABLE s 3USPENSION (Z TO THE EARS AND HAS A RANGE OF MPH KPH s $RIVELINE (Z AND UP s $IFFERENTIAL COMPONENTS (Z $RONING ,OW 3PEED n ! LONG DURATION LOW PITCHED NOISE THAT IS NON DIRECTIONAL AND HAS A .OISE n 4HE UNPLEASANT OR UNEXPECTED SOUND RANGE OF UP TO MPH KPH CREATED BY A VIBRATING OBJECT $RONING -IDDLE 3PEED n ! LONG DURATION LOW /RDER n 4HE NUMBER OF DISTURBANCES CREATED IN PITCHED NOISE THAT IS NON DIRECTIONAL AND HAS A ONE REVOLUTION OF A COMPONENT RANGE OF TO MPH TO KPH 0HASE n 4HE POSITION OF A VIBRATION CYCLE RELATIVE %LECTRONIC 6IBRATION !NALYZER )) %6! )) n !N TO ANOTHER VIBRATION CYCLE IN THE SAME HERTZ RATE ELECTRONIC .6( DIAGNOSTIC TOOL THAT MEASURES TIME FRAME FREQUENCY AND AMPLITUDE
'LOSSARY 0HASE n 4HE CYCLE PATTERN OF TWO OR MORE VIBRATIONS THAT OVERLAP AND COMBINE TO INCREASE OR DECREASE THE OVERALL MAGNITUDE
3TATIC "ALANCE n 4HE METHOD OF BALANCING A TIRE AND WHEEL ASSEMBLY IN A SINGLE PLANE 3TATIC BALANCING REMOVES ONLY THE LATERAL SIDE TO 0ITCH n 4HE PHYSICAL QUALITY OF SOUND THAT RELATES SIDE WOBBLE IMBALANCE AND THE TIRE AND WHEEL ASSEMBLY COULD POSSIBLY HAVE A RADIAL UP AND TO THE FREQUENCY OF THE WAVE DOWN VIBRATION 2ADIAL &ORCE 6ARIATION 2&6 n ! MEASUREMENT 4ORQUE 3ENSITIVE 6IBRATION OR .OISE n ! OF THE TIRES UNIFORMITY UNDER LOAD IN REGARDS VIBRATION OR NOISE THAT IS SENSITIVE TO DIFFERENT TO THE VARIATION OF THE LOAD ACTING TOWARDS THE LOADS AND TORQUE APPLIED TO THE DRIVE TRAIN OF A CENTER OF THE TIRE COMMONLY REFERRED TO AS THE VEHICLE 4HE VIBRATION OR NOISE CHANGES WHEN THE TIREgS SIDEWALL VARIATION THROTTLE POSITION OR TRANSMISSION GEARING IS USED 2ADIAL 2UNOUT n ! CONDITION WHERE A ROTATING DURING A ROAD TEST TO CHANGE THE TORQUE APPLIED COMPONENT DOES NOT ROTATE IN A TRUE PLANE 4HE TO THE DRIVE TRAIN COMPONENT MOVES UP AND DOWN ON ITS ROTATIONAL 6IBRATION n 4HE REPETITIVE MOTION OF AN OBJECT AXIS BACK AND FORTH OR UP AND DOWN WHICH MAY BE 2ESONANCE n 4HE TENDENCY OF A SYSTEM TO FELT OR HEARD RESPOND INCREASINGLY TO A COMPELLING FORCE 7HEEL $IAMETER n 4HE DIMENSION OF A WHEEL OSCILLATING AT OR NEAR THE NATURAL FREQUENCY OF MEASURED ON THE INSIDE OF THE WHEEL AT THE THE SYSTEM 4HIS CAUSES A SUDDEN AND LARGE BEAD SEAT AREA VIBRATION 2OAD .OISE n ! NOISE THAT OCCURS WHILE DRIVING ON GRAVEL OR ROUGHLY PAVED ROADS AT ALL VEHICLE SPEEDS OR WHEN A VEHICLE IS COASTING 3HAKE ,ATERAL n ! SIDE TO SIDE VIBRATION OF THE BODY SEATS AND STEERING WHEEL 3HAKE 6ERTICAL n !N UP AND DOWN VIBRATION OF THE BODY SEATS AND STEERING WHEEL 3HIMMY (IGH 3PEED n ! VIBRATION THAT CAUSES THE STEERING WHEEL TO OSCILLATE WHEN DRIVING ON SMOOTH ROADS AT HIGH SPEEDS 3HIMMY ,OW 3PEED n ! VIBRATION THAT CAUSES THE STEERING WHEEL TO OSCILLATE WHEN DRIVING ACROSS A BUMP AT LOW SPEEDS 3OURCE #OMPONENT n 4HE COMPONENT THAT IS DIAGNOSED AS BEING THE ROOT CAUSE OF A VIBRATION OR NOISE CONCERN 3OUND n 4HE RESULT OF A VIBRATING DISTURBANCE OF AN OBJECT WHICH PRODUCES WAVES THAT TRANSMIT OUT FROM THE SOURCE
#ONCERN DISAPPEARS OR IS DIMINISHED AFTER THE CAR HAS BEEN DRIVEN AWHILE
#HECK TIRES FOR 4EMPORARY &LAT 3POTTING 4IRES CAN BECOME TEMPORARY FLAT SPOTTED WHEN A VEHICLE HAS BEEN DRIVEN AND THEN PARKED ON A COLD SURFACE 4HIS MAY HAPPEN IN COLD CLIMATES AS WELL AS WARM CLIMATES 6EHICLES PARKED FOR LONG PERIODS OF TIME ANDOR STORED WITH LOW AIR PRESSURE ARE ALSO SUSCEPTIBLE TO FLAT SPOTTING
&ELT WHILE BRAKING
#HECK s "RAKE COMPONENTS s 3TEERING COMPONENTS s 3USPENSION COMPONENTS s 2ELEVANT 4ECHNICAL "ULLETINS
огромный архив документации по автомобилям Volkswagen, Skoda, Seat, Audi
Volkswagen Technical Site: http://vwts.ru http://vwts.info #HECK DRIVE TRAIN FOR s 0ROP SHAFT MISALIGNMENT s $AMAGED AXLE SHAFTS#6 JOINTS s 7ORN WHEEL BEARINGS s 2EAR DIFFERENTIAL PERFORMANCE
#HECK TIRES FOR s (IGH 2ADIAL &ORCE 6ARIATION 2&6 s )MBALANCE s )RREGULAR WEAR s !BNORMAL PRESSURE
#HECK WHEELS FOR s $IRT MUD SNOW OR ICE BUILD UP s $AMAGE s -ISSING OR EXCESSIVE WHEEL WEIGHTS s ,OOSE WHEEL BOLTS s 0ROPER WHEEL TORQUE s %XCESSIVE RUNOUT
6IBRATION IS FELT AT A CERTAIN VEHICLE SPEED
#HECK #HASSIS FOR s $AMAGED OR MISALIGNED ENGINE AND TRANSMISSION MOUNTS s 0ROPER %LECTRO (YDRAULIC MOUNT OPERATION s $AMAGED OR MISALIGNED EXHAUST SYSTEM AND COMPONENTS
#HECK %NGINE FOR s -ISFIRES s !CCESSORY VIBRATIONS s #AMSHAFT CRANKSHAFT AND INTERMEDIATE SHAFT IMBALANCE
#HECK DRIVE TRAIN FOR s 0ROP SHAFT MISALIGNMENT s $AMAGED AXLE SHAFTS s $AMAGED #6 JOINTS s 2EAR DIFFERENTIAL PERFORMANCE s 0ROPER TORQUE CONVERTER PERFORMANCE
6IBRATION IS FELT AT A CERTAIN ENGINE SPEED
)S IT FELT THROUGH SEATVEHICLE FLOOR PAN n 3TART WITH REAR AXLE
$IAGNOSE ACCORDING TO CONDITIONS LISTED BELOW
)S IT FELT THROUGH THE STEERING WHEEL n 3TART WITH FRONT AXLE
2OAD TEST TO VERIFY CONCERN
#HECK VEHICLE HISTORY PRIOR TO DIAGNOSIS AND USE .6( 330 FOR IN DEPTH DIAGNOSIS
$IAGNOSTIC &LOW #HART
Vorsprung durch Technik
All rights reserved. Technical specifications subject to change without notice. Audi Australia
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