building a borg warner 1350-1354 doubler system

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uilding a Borg Warner 1350-1354 Doubler System

Bui ld ing a Borg Warner 1350-1354 Doubler System

Wri t t en and phot ographed by Evan VaughanProcess deve loped by Todd Mc Intosh

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

downloading and/or reading this you agree to assume all risks and liabilities related to building and operating a doubler, including

t not limited to loss of vehicle, accidents, or injuries. If you have any questions you should consult a certified professional.

Preface [Next] [Prev] [Top]

hy build a doubler?

s tires get larger and larger, more gear reduction is required to provide enough torque at low speed to turn

em. Changing differential ratios provides more reduction, but Ranger-based vehicles (RBV) are limited to

ound 5.13 gears before the pinion gets too small and weak. 5.13s though helpful, provide only limited reduction.

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.

doubler will take you from 35 to 85 while still providing good highway RPM.

nefits

ttp://www.sbe.mtu.edu/users/etvaugha/explorer/doubler1.htm (1 of 17) [12/29/2008 3:32:54 PM]

http://www.sbe.mtu.edu/users/etvaugha/b2explorer/index.htm




oublers provide a massive amount of low-end torque and a very low crawl ratio. They provide the driver with true

wheel low range, as the doubler case can be put in LO and the transfer case in 2 HI. Trucks with a doubler have

new range of off-road gears. A manual transmission with a doubler provides the driver with 18 different gears;

forward and 3 reverse.

asics

his article will describe how to put a Borg Warner (BW) 1350 transfer case in front of an existing BW1354. This

done by splitting the 1350 and keeping only the front half, then cutting the front output housing off of that front

lf. Then the 1350 half is connected to the 1354 by means of a steel plate between the two. A custom shaftnnects the two cases. To compensate for the 6” addition, the front and rear drive shafts must be lengthened

d shortened respectively.

osts

he system can be built for around $400. This includes parts, materials, and tools. Costs will vary for each person

d by location. You may already have all the materials lying around in your garage or you may have to

y everything. You might have a buddy with an old Ranger that lets you grab the 1350, or you might have a stuck-

yard that charges a few hundred for a case. Plan on spending at least a couple hundred on the entire project. For

e it cost around $300 total, but I already had all the tools.

ho should build a doubler?

nly those with advanced mechanical experience should attempt this. It is harder than rebuilding an engine.

ne mistake and the whole setup could be shot. This project requires patience and problem solving. Plan on at least

working days to get it done.

his is only a guide. Each setup may be different. There are so many steps in the project that this would

rn into 100+ pages, so each step is not necessarily listed.

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

omponents

ou will need a Borg Warner 1350 manual shift transfer case. You cannot use an electric shift case. Your best bet

finding a manual 1350 is a 1980s 4WD Ranger.

ou also need an RBV 4x4 transmission output shaft. You only need the end. I went to a junkyard and asked if

ey had any junk RBV transmissions. Then I had them cut off the shaft with a torch.

ols

ormal tools, i.e. socket set, wrenches, c-clamps

hole saw

rill with high-quality metal bits

ngle grinder with cutting and grinding blades

8” 16 pitch tap

you’re going to shorten/lengthen your drive shafts yourself you’ll need a chop saw and a welder.





aterials

”x12”x1/2” steel plate

TV sealant

Weld

ake parts cleaner

ags

3/8” bolts, 1.5” long

3/8” bolts, 1/2” long

ther

ou’ll want to find another transfer case skid plate to protect the new case.

order for the doubler assembly to fit without major body modification, you need a 3” body lift on Bronco II

ucks, and a 2” body lift on Explorer and Ranger vehicles.

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

his is one of the easiest parts of the job.

emove the center bolts holding the two halves of the case and pull it apart.

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





he rear housing with all the components is junk.

Making the Sector Shaft [Next] [Prev] [Top]

his is a part where you’ll be heading to the local machine shop, unless you have an arbor press and a metal lathe.

he cost for this should be between $50 and $100.

ake the sector shaft (the main shaft inside the case) and your 4x4 output.

ell them what the application is. Tell them the shaft needs to be build to handle the most torque possible. They

ed to first cut down the sector shaft, and then bore it out. Then they need to lathe down the 4x4 output and press

e two together. Finally, the two need to be welded together. You’ll start with this:





4 output top, sector shaft bottom. Remove that little ATF pump and discard it.

nd you’ll end up with this:





s for the length, you cut the sector shaft off at the gear. The 4x4 output goes in with the splines ending right

here the sector shaft begins. The total length of the shaft should be

7/8” and the output spline length should be 2 1/16”.

mportant:

his is probably the weakest link in this doubler setup. When welding the shaft, it's important to heat both pieces

steel to around 500 degrees F prior to welding. After the welding is complete, allow the shaft to slowly cool in

preheated 500 degree oil bath.

dditionally, do not put the doubler case in LO and the transfer case in HI. This puts excessive strain on the

ubler sector shaft. If you want to use single LO range, use the transfer case.

you abide by the above rules, you should have no problems. I've had my doubler in for about a year, and have

d the skinny pedal to the rug many times; snapping axle shafts and drive shafts. The doubler shaft has stoodong. If you're still skeptical on this two-piece shaft, I have seen people get custom one-piece shafts cut and

rned for as little as $100.

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





ou should have the front 1350 housing with the planetary set removed. The next step is to cut the front

tput housing off. As looking at the above picture, you want to keep the bottom hole and cut through the top

le. Below is what you should end up with:





hrow away the housing on the right. You now officially have a doubler housing. There is a ½” gap at the end of

e case, this can be filled in with some of the ½” plate bolted in and sealed with JB Weld.





rill and tap drain/fill holes in the top and bottom of the case. You can thread a short bolt

to each of the two holes as a plug. Be sure to seal the drain plug/bolt with RTV or it will leak.

Plate Fabrication [Next] [Prev] [Top]

ne up the doubler housing on the plate. Make a center mark on the plate through the input hole and get to work

th the 5” hole saw. It will take at least 20 minutes to cut through the plate. Use cutting oil and allow for the drill

cool from time to time.





nce 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

e plate. These will thread into the plate. The remaining case boss holes around the 5” hole will thread into the

se from the opposite side.





ou can clean out the case and reinstall the front plate. Above: the first of the outer two holes has been drilled

d tapped into the plate. The bolt is threaded in on the bottom right.

ext, drill 7/16”

holes for bolts to thread into the case from the opposite side as shown below. You can use theock bolts that used to hold the two halves of the 1350 together.





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





ou’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.

Preparing the 1354 [Next] [Prev] [Top]

he 1354 front plate has to be ground down in three places in order to fit over the bolt heads going into the

50. You’ll need to remove the 1354 front plate and see what needs to be ground down.

nce you get the plate seated you can drill the holes into the steel plate and tap them. You may wish to clock up

e transfer case a little if you think you’ll have drive shaft clearance issues with the radius arm cross member.

ne bolt goes through the plate and threads into the 1354, the remaining go from the 1354 front plate into the

eel plate. These are the 1.5” long 3/8” dia. bolts you purchased. You’ll have to drill out the threads in the bosses,

the stock setup has bolts thread into the 1354 plate from the transmission.

nce the 1354 breather tube output is now right in front of the plate, you’ll need to cut down the existing fitting

order to be able to fit a hose over it. You can also find and thread in a 90 degree fitting.





dditionally some minor grinding may need to be done on the actual case for bolt head clearance. Clearance issues

e huge in this project. Basically, grind where the need arises.

Assembly/Installation [Next] [Prev] [Top]

is recommended that you do a trial assembly to make sure everything fits before RTV sealing it.

rder:

Begin with both front plates removed from the cases

Bolt the doubler case onto the plate

Bolt the 1354 front plate onto the steel plate, with the 1354 plate-to-case bolts in place

Assemble the internals in the doubler case

Install the doubler case front plate, check to make sure the case shifts ok

Connect the 1354 to its front plateFill the doubler case to the top with gear oil; the transfer case can be filled with ATF after installation





ctured above is the completed Borg Warner 1350/1354 doubler system.

hen you install the case you may run into clearance issues. On Explorer 2-door vehicles, you’ll need to cut down

e front end of the gas tank skid plate. On Bronco II trucks, a body cross member interferes with the cases. You

ay need to cut away part of the cross member. A body lift makes fitment much easier. A 3” body lift is

commend on Bronco II trucks, and a 2” on Explorers. Anything less and you may end up cutting a very large

unk out of the floorboards in order to fit the assembly.

o not attempt to lift the cases up by yourself. The assembly is very heavy and awkward. It ’ s very difficult to

lance on a jack. Find another person who can help.

he assembly is installed under the truck. The shifting linkage for each case still needs to be connected. You’ll need

bolt an additional skid plate behind the stock skid plate in order to protect the transfer case.

Driveshaft Changes [Next] [Prev] [Top]

our front shaft will need to be lengthened and the rear shortened, both by about 6”.

ou 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.

ut 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

over the shaft, and weld it on.





or the rear: Grind off the weld where the male splines for the slip yoke come out of the driveshaft. Cut the

cessary amount off the shaft, and then hammer out the splined cup. Carefully and evenly re-weld it to the

orter shaft. Either of the two shafts can be dynamically balanced by filling them with some oil.

ote regarding the shift linkage: When under load in LO range, the doubler case is going to want to jump out of

ar. This can be addressed by building or swapping in some locking shift linkage. If you already have a manual shiftcase in the truck, the existing linkage will connect right to the doubler with little or no modification. Then you can

t 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

own.

you're looking to get on the trail right away, the solution can be as simple as a lever attached to the doubler case

ift input, with a bungee cord to hold it in gear.

Copyright (c) 2007, Evan Vaughan

building a borg warner 1350-1354 doubler system

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