Building A Borg Warner 1350-1354 Doubler System

Building a Borg Warner 1350-1354 Doubler System

Building a Borg Warner 1350-1354 Doubler System Written and photographed by Evan Vaughan Process developed by Todd McIntosh

Table of Contents 1. Preface 2. Tool and Material Requirements 3. Splitting the 1350 4. Making the Sector Shaft 5. Cutting the 1350 6. Plate Fabrication 7. Preparing the 1354 8. Assembly/Installation 9. Driveshaft Changes

By downloading and/or reading this you agree to assume all risks and liabilities related to building and operating a doubler, including but not limited to loss of vehicle, accidents, or injuries. If you have any questions you should consult a certified professional.

1. Preface [Next] [Prev] [Top] Why build a doubler? As tires get larger and larger, more gear reduction is required to provide enough torque at low speed to turn them. Changing differential ratios provides more reduction, but Ranger-based vehicles (RBV) are limited to around 5.13 gears before the pinion gets too small and weak. 5.13s though helpful, provide only limited reduction. If you’re running 3.73 gears and an M5OD transmission, you’ll go from 35 to 47 in final crawl ratio with 5.13 gears. A doubler will take you from 35 to 85 while still providing good highway RPM. Benefits

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Building a Borg Warner 1350-1354 Doubler System

Doublers provide a massive amount of low-end torque and a very low crawl ratio. They provide the driver with true 2-wheel low range, as the doubler case can be put in LO and the transfer case in 2 HI. Trucks with a doubler have a new range of off-road gears. A manual transmission with a doubler provides the driver with 18 different gears; 15 forward and 3 reverse. Basics This article will describe how to put a Borg Warner (BW) 1350 transfer case in front of an existing BW1354. This is done by splitting the 1350 and keeping only the front half, then cutting the front output housing off of that front half. Then the 1350 half is connected to the 1354 by means of a steel plate between the two. A custom shaft connects the two cases. To compensate for the 6” addition, the front and rear drive shafts must be lengthened and shortened respectively. Costs The system can be built for around $400. This includes parts, materials, and tools. Costs will vary for each person and by location. You may already have all the materials lying around in your garage or you may have to buy everything. You might have a buddy with an old Ranger that lets you grab the 1350, or you might have a stuckup yard that charges a few hundred for a case. Plan on spending at least a couple hundred on the entire project. For me it cost around $300 total, but I already had all the tools. Who should build a doubler? Only those with advanced mechanical experience should attempt this. It is harder than rebuilding an engine. One mistake and the whole setup could be shot. This project requires patience and problem solving. Plan on at least 7 working days to get it done. This is only a guide. Each setup may be different. There are so many steps in the project that this would turn into 100+ pages, so each step is not necessarily listed.

2. Tool and Material Requirements [Next] [Prev] [Top]

Components You will need a Borg Warner 1350 manual shift transfer case. You cannot use an electric shift case. Your best bet in finding a manual 1350 is a 1980s 4WD Ranger. You also need an RBV 4x4 transmission output shaft. You only need the end. I went to a junkyard and asked if they had any junk RBV transmissions. Then I had them cut off the shaft with a torch. Tools Normal tools, i.e. socket set, wrenches, c-clamps 5” hole saw Drill with high-quality metal bits Angle grinder with cutting and grinding blades 3/8” 16 pitch tap If you’re going to shorten/lengthen your drive shafts yourself you’ll need a chop saw and a welder. http://www.sbe.mtu.edu/users/etvaugha/explorer/doubler1.htm (2 of 17) [12/29/2008 3:32:54 PM]

Building a Borg Warner 1350-1354 Doubler System

Materials 12”x12”x1/2” steel plate RTV sealant JB Weld Brake parts cleaner Rags 6 3/8” bolts, 1.5” long 2 3/8” bolts, 1/2” long Other You’ll want to find another transfer case skid plate to protect the new case. In order for the doubler assembly to fit without major body modification, you need a 3” body lift on Bronco II trucks, and a 2” body lift on Explorer and Ranger vehicles.

3. Splitting the 1350 [Next] [Prev] [Top]

This is one of the easiest parts of the job. Remove the center bolts holding the two halves of the case and pull it apart.

You can then remove the bolts holding the front plate and pull that off; the planetary set will come out with it.

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Building a Borg Warner 1350-1354 Doubler System

The rear housing with all the components is junk.

4. Making the Sector Shaft [Next] [Prev] [Top] This is a part where you’ll be heading to the local machine shop, unless you have an arbor press and a metal lathe. The cost for this should be between $50 and $100. Take the sector shaft (the main shaft inside the case) and your 4x4 output. Tell them what the application is. Tell them the shaft needs to be build to handle the most torque possible. They need to first cut down the sector shaft, and then bore it out. Then they need to lathe down the 4x4 output and press the two together. Finally, the two need to be welded together. You’ll start with this:

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Building a Borg Warner 1350-1354 Doubler System

4x4 output top, sector shaft bottom. Remove that little ATF pump and discard it. And you’ll end up with this:

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Building a Borg Warner 1350-1354 Doubler System

As for the length, you cut the sector shaft off at the gear. The 4x4 output goes in with the splines ending right where the sector shaft begins. The total length of the shaft should be 5 7/8” and the output spline length should be 2 1/16”. Important: This is probably the weakest link in this doubler setup. When welding the shaft, it's important to heat both pieces of steel to around 500 degrees F prior to welding. After the welding is complete, allow the shaft to slowly cool in a preheated 500 degree oil bath. Additionally, do not put the doubler case in LO and the transfer case in HI. This puts excessive strain on the doubler sector shaft. If you want to use single LO range, use the transfer case. If you abide by the above rules, you should have no problems. I've had my doubler in for about a year, and have had the skinny pedal to the rug many times; snapping axle shafts and drive shafts. The doubler shaft has stood strong. If you're still skeptical on this two-piece shaft, I have seen people get custom one-piece shafts cut and turned for as little as $100.

5. Cutting the Case [Next] [Prev] [Top]

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Building a Borg Warner 1350-1354 Doubler System

You should have the front 1350 housing with the planetary set removed. The next step is to cut the front output housing off. As looking at the above picture, you want to keep the bottom hole and cut through the top hole. Below is what you should end up with:

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Building a Borg Warner 1350-1354 Doubler System

Throw away the housing on the right. You now officially have a doubler housing. There is a ½” gap at the end of the case, this can be filled in with some of the ½” plate bolted in and sealed with JB Weld.

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Building a Borg Warner 1350-1354 Doubler System

Drill and tap drain/fill holes in the top and bottom of the case. You can thread a short bolt into each of the two holes as a plug. Be sure to seal the drain plug/bolt with RTV or it will leak.

6. Plate Fabrication [Next] [Prev] [Top] Line up the doubler housing on the plate. Make a center mark on the plate through the input hole and get to work with the 5” hole saw. It will take at least 20 minutes to cut through the plate. Use cutting oil and allow for the drill to cool from time to time.

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Building a Borg Warner 1350-1354 Doubler System

Once the hole is cut you can line the case back up on the plate. Drill out and tap the two most outer boss holes into the plate. These will thread into the plate. The remaining case boss holes around the 5” hole will thread into the case from the opposite side.

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Building a Borg Warner 1350-1354 Doubler System

You can clean out the case and reinstall the front plate. Above: the first of the outer two holes has been drilled and tapped into the plate. The bolt is threaded in on the bottom right. Next, drill 7/16” holes for bolts to thread into the case from the opposite side as shown below. You can use the stock bolts that used to hold the two halves of the 1350 together.

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Building a Borg Warner 1350-1354 Doubler System

Finally, place the doubler case on the plate and cut it out.

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Building a Borg Warner 1350-1354 Doubler System

You’ll need to cut down the shaft that the shift fork rides on and grind a recessed hole in the plate for it to sit.

7. Preparing the 1354 [Next] [Prev] [Top] The 1354 front plate has to be ground down in three places in order to fit over the bolt heads going into the 1350. You’ll need to remove the 1354 front plate and see what needs to be ground down. Once you get the plate seated you can drill the holes into the steel plate and tap them. You may wish to clock up the transfer case a little if you think you’ll have drive shaft clearance issues with the radius arm cross member. One bolt goes through the plate and threads into the 1354, the remaining go from the 1354 front plate into the steel plate. These are the 1.5” long 3/8” dia. bolts you purchased. You’ll have to drill out the threads in the bosses, as the stock setup has bolts thread into the 1354 plate from the transmission. Since the 1354 breather tube output is now right in front of the plate, you’ll need to cut down the existing fitting in order to be able to fit a hose over it. You can also find and thread in a 90 degree fitting.

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Building a Borg Warner 1350-1354 Doubler System

Additionally some minor grinding may need to be done on the actual case for bolt head clearance. Clearance issues are huge in this project. Basically, grind where the need arises.

8. Assembly/Installation [Next] [Prev] [Top] It is recommended that you do a trial assembly to make sure everything fits before RTV sealing it. Order: 1. Begin with both front plates removed from the cases 2. Bolt the doubler case onto the plate 3. Bolt the 1354 front plate onto the steel plate, with the 1354 plate-to-case bolts in place 4. Assemble the internals in the doubler case 5. Install the doubler case front plate, check to make sure the case shifts ok 6. Connect the 1354 to its front plate 7. Fill the doubler case to the top with gear oil; the transfer case can be filled with ATF after installation

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Building a Borg Warner 1350-1354 Doubler System

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Building a Borg Warner 1350-1354 Doubler System

Pictured above is the completed Borg Warner 1350/1354 doubler system. When you install the case you may run into clearance issues. On Explorer 2-door vehicles, you’ll need to cut down the front end of the gas tank skid plate. On Bronco II trucks, a body cross member interferes with the cases. You may need to cut away part of the cross member. A body lift makes fitment much easier. A 3” body lift is recommend on Bronco II trucks, and a 2” on Explorers. Anything less and you may end up cutting a very large chunk out of the floorboards in order to fit the assembly. Do not attempt to lift the cases up by yourself. The assembly is very heavy and awkward. It’s very difficult to balance on a jack. Find another person who can help.

The assembly is installed under the truck. The shifting linkage for each case still needs to be connected. You’ll need to bolt an additional skid plate behind the stock skid plate in order to protect the transfer case.

9. Driveshaft Changes [Next] [Prev] [Top] Your front shaft will need to be lengthened and the rear shortened, both by about 6”. You can have a shop do this or do it yourself. You’ll need a chop saw and a welder if you want to do it yourself. Cut the front shaft right in the middle. Find a piece of pipe that has ¼” thick walls and is the right diameter to fit in or over the shaft, and weld it on. http://www.sbe.mtu.edu/users/etvaugha/explorer/doubler1.htm (16 of 17) [12/29/2008 3:32:54 PM]

Building a Borg Warner 1350-1354 Doubler System

For the rear: Grind off the weld where the male splines for the slip yoke come out of the driveshaft. Cut the necessary amount off the shaft, and then hammer out the splined cup. Carefully and evenly re-weld it to the shorter shaft. Either of the two shafts can be dynamically balanced by filling them with some oil. Note regarding the shift linkage: When under load in LO range, the doubler case is going to want to jump out of gear. This can be addressed by building or swapping in some locking shift linkage. If you already have a manual shift t-case in the truck, the existing linkage will connect right to the doubler with little or no modification. Then you can set up some linkage for the t-case, but you don't have to worry about locking linkage; the t-case will stay in gear on its own. If you're looking to get on the trail right away, the solution can be as simple as a lever attached to the doubler case shift input, with a bungee cord to hold it in gear.

Copyright (c) 2007, Evan Vaughan

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