YJ Brake Upgrades
**Rear Disc Brakes on D44**
**Master Cylinder & Prop Valve Swap on 1994 Jeep Wrangler**

Vehicle Information: 1994 Jeep Wrangler w/ 4.0L engine and Manual transmission. Dana 44 axles from a 1989 Jeep Grand Wagoneer with front discs and rear drum brakes.

Why change the brakes??: For many years - We've had the Dana 44's (disc / drums) on our Jeep and the brakes worked fine for the amount of street driving and trail riding we've done. The stock master cylinder (1" bore) was capable of stopping the 11" diameter brakes with 35" tires. I will admit - the pedal did go further to the floor than what it should AND we never dared to test a panic stop. The rear drums were rebuilt and the shoes never wore evenly before and even after we replaced the adjusters. We were always manually adjusting and re-adjusting the shoes and adjusting the emergency brake cable for the e-brake to work properly. Improving the brakes has always been on our minds over the years. Instead of just throwing in a bigger bore master cylinder - I wanted to get rid of the drum brakes completely.

Brake Research: I spent A LOT of time researching and learning how the brake system works. The differences between disc/drums and the differences in master cylinders, what the booster does, and how the proportioning works. When converting drums to disc brakes - there are differences in the Master cylinders as well as the proportioning and valving. Drum brakes require residual pressure which is valved inside the master cylinder. Drum brakes also require metering & proportioning, which is usually found inside the combination valve. Disc brakes don't require residual pressure or metering - but they do require proportioning. What I've learned - gave me a better understanding of what I needed to look for in parts to make the whole system work together. Hopefully - my research will have paid off.

Disc Brake Kits - Long Story Short: My vehicle is street legal and keeping the emergency brake was important. I spent more time researching what other people have done and what setups were available. I don't take brakes lightly - my life depends on them. I discussed my plans with Otter (Bryan @ Whaley Enterprises) and he gave me some suggestions on what works well and what doesn't. I requested Otter do the installation of the brake kit - to make sure everything is done properly.

The Disc Brake kit :
If you have Grand Wagoneer rear D44 axle - do not get a Teraflex disc brake kit. It will not work with this axle.

Instead - we went with:

TSM Manufacturing disc brake kit for Jeep '74-'92 Full Size Cherokee, Wagoneer, J-10 (wheel bolt pattern 6 lugs x 5 1/2 inch circle). As seen here: http://www.tsmmfg.net/2460.html. Along with the kit - we ordered Part No. 3110 New Calipers with parking brakes AND Part No. 3702-8 Braided Stainless hose 8".

The Master Cylinder:
A rebuilt master cylinder for a 1978 Mercury Marquis with 4 wheel discs and hydro boost. Purchased at my local auto store. This master cylinder has 1.125" bore. Advance Auto Part # 101603 (rebuilt unit)

The Proportioning Valve:
A proportioning valve from a 1998 Jeep Grand Cherokee (ZJ) with 4 wheel disc brakes purchased from http://www.firstclass4x4.com/

Other Parts Needed:
Other than brake fluid.....You'll have to either buy new fittings, re-use your current fittings, or buy adapters. If you're not using adapters - you'll need to have hard brake lines cut and re-flared OR have new lines made up.

The coiled hard brake lines that connect the Master Cylinder to the Combination valve have 2 different fittings - a smaller (3/8") and larger (1/2"). On the stock YJ lines - each coiled hard line has one large and one small fitting opposite of each other on the ends. The Mercury Marquis master cylinder inlet fittings are opposite of the YJ fittings.

For this project - you will have two coiled hard lines - one will have both small fittings while the other coiled line will have both larger fittings on each end. I decided to get all new fittings and have the lines cut and re-flared.
I bought 2 of the smaller (3/8") fittings from a local auto store.
I bought 2 of the larger (1/2") fittings from the dealership. I couldn't find these larger fittings anywhere and none of the guys at all the auto stores had ever seen a fitting of that size.
I took the coiled lines & fittings to the dealer - paid them $25 to cut and re-flare the ends with the proper fittings on each end.



Click on the image for a larger picture. You can click HERE for installation instructions and pricing information. These rear calipers (with ebrake) are from a 79-85 El-Dorado, Riviera, and Toronado and 80-85 Seville.

Unfortunately - I did not install the disc brake kit. I do not have detailed information on how to install them. However - I did have to adjust the calipers and adjust the e-brake after it was all installed.

Picture of the e-brake setup included on the caliper. You'll also notice the hard line (left) going through a bracket (welded to axle tube) and connects to the stainless braided line. Click image for a larger picture.

Caliper adjustment and e-brake adjustment are VERY critical to making your brakes work properly and effectively.

Using the e-brake on a regular basis is mandatory to keeping the calipers adjusted properly as the shoes wear.

You will need to remove the old bearings off your axle shaft.

While pressing new bearings on - there is a bearing pre-load spacer that is installed between the retainer plate and the bearing.

The bearing retainer plate in this picture is not original to the axle. The stock D44 retainer plates will work fine.

Axle Flange

After installing the entire disc brake kit and before you introduce fluid into the calipers - remove the e-brake cable at the Adjuster. This will give you slack in the cable so it'll be easier to remove (See below).

The Adjuster on the YJ's are located on the inside frame rail just below the drivers side door.

Simply remove the Adjustment Nut and let the cables hang freely with the bracket. Click on the picture to the left for a larger image.

Remove the cable from the Caliper Lever. Be careful when handling and removing the spring.


Ebrake Diagram

The Caliper Adjustment Lever is what adjusts the caliper - ensuring the brakes pads are in proper placement to the rotor for effective braking. The lever must be cycled in order to keep the calipers adjusted properly. The only way the lever is cycled, is by the usage of the e-brake.

INITIAL TESTING : After you have removed the ebrake cable - kneel in front of the rotor and give it a gentle shake (as if you were removing it).. Do you notice any PLAY between the pads & rotor?? Make note of this.

For the TSM kit caliper adjustment - You'll notice the Adjustment Lever has a STOP position (where it rests on the caliper). Grab the adjustment lever and push it as far as you can away from the STOP (forward stroke). Then return it back to the stop position. Do this as many times as needed - each time - the stroke should be less and less. Stop cycling when you've reached 3/8" to 1/2" between the lever and the STOP at FULL forward stroke of the lever.

AFTER TESTING: After you have reached the above adjustments - kneel in front of the rotor again (like above) and give it a gentle shake again. The amount of play you had previously - should be completely gone. There shouldn't be any play between the pads and the rotor. Spin the rotor by hand - it should spin with minimal effort but you will feel some resistance from the pads.

Do this to both sides and then attach you emergency brake cables. Again, be careful when handling and installing the spring.

Re-install the E-brake Adjuster Nut. Do not thread it on too much. This Adjustment nut is what tightens or loosens your e-brake cable.


The Adjustment nut should be at the end of the threads on the Adjustment Rod. Take a look at your Caliper levers and take notice to their position. The levers should be sitting directly on the STOP point.

At this time - begin to tighten the Adjustment Nut slowly (one revolution at a time) until you have enough room between the STOP and the Lever to just barely fit a piece of standard printer paper between them.

Master Cylinder Swap
I purchased a Rebuilt Master Cylinder for a 1978 Mercury Marquis with 4 wheel disc brakes AND hydro boost. It was a bit difficult to find this exact part - as some of the auto stores do not have the 'hydro boost' listed in their computers. I finally found the right one locally. This master cylinder bolts directly up to the Jeep YJ stock booster - no other adjustments are needed. If you'll notice on the left picture - the amount of space between the reservoir and the mounting plates on both master cylinders. The Marquis master cylinder sits a lot closer to the booster and doesn't leave much room for the clamp to swing freely. You will need to carefully do some 'bending' of the clamp to make it hold the lid on. See pictures of both master cylinders below. Click Image for a larger picture

Stock YJ Master cylinder on the LEFT.
Stock YJ Master cylinder on the LEFT.

Before installing the Master Cylinder - Read this entire write-up to make sure you have everything else (lines & prop valve) 'ready to install'. You will need to bench bleed the master cylinder just prior to installation.

Master Cylinder Fittings
As seen in the above picture (left) - the coiled lines will need to be changed to have the proper fittings in place. If you'll also notice - there are 4 fittings sitting on the right. Two of these fittings are the smaller (3/8") fittings and both of these will be installed on the coiled line that feed the rear brake lines . The other two fittings (on the left) are the larger (1/2") fittings. These will be installed on the coiled lines that feed the front brake lines (closest to the booster).
I purchased the smaller fittings from a local auto store and the larger fittings from the dealer. I also paid the dealership $25 to cut & re-flare my original coiled lines in the exact orientation I needed them to be in.

ZJ Proportioning Valve
I ordered a 1998 Jeep Grand Cherokee (with 4 wheel discs) proportioning valve. The ZJ proportioning valve is almost a direct bolt-in to the YJ hard lines.

I ordered my ZJ proportioning valve from First Class 4x4 - http://www.firstclass4x4.com/
First Class 4x4 is a junkyard that will sell used parts over the internet and ship them to you.

You'll need to remove the ZJ bracket (black steal bracket).
You'll want to remove the plug from the ZJ prop valve (seen in the picture). You'll want to remove the fitting (Front Line) from the YJ prop valve (seen in the picture). This Front Line fitting from the YJ - will need to be threaded into the ZJ valve in the same place the plug was.

ZJ YJ Prop
Final Installation:
Before bench bleeding or installing the master cylinder, I installed the ZJ proportioning valve in the Jeep and installed the coiled hard lines to the top side of the prop valve. These were ready to go for a 'quick' connection to the master cylinder with minimal fluid loss.

Before installing the Master cylinder on the vehicle - make sure you bench bleed it very carefully. Carefully install the master cylinder onto the vehicle. Attach the hard lines to the master cylinder as carefully ( and quickly) trying not to lose much fluid. Tighten the master cylinder onto the booster and tighten all fittings.

It's a good idea to have a bottle of "Brake Kleen" (or similar cleaner) to wash the brake fluid off. Brake fluid can remove paint - so be very careful not to get it on your vehicle.

Attach the wiring & top off the fluid reservoir. Clean the area with Brake Kleen or similar solvent and get ready to bleed the brakes. And bleed the brakes again...and again....Bleeding Brakes

MasterCylinder Top
New Prop Valve

Final *Test Drive*
The initial test drive was actually a good one - although we thought it should be better - the pedal went down farther than we expected. We drove back home and checked for leaks. We found a couple very very small amounts of fluid on the rear disc brake bolts - tightened them down. We also found some leaks up by the master cylinder fittings. After tightening everything down - bled the brakes again. Note: Anytime you have a leak in the system, you've allowed air to get into the system. After discovering any leaks - you should always bleed the brakes again.

Master Cylinder Lid:
If you'll remember - the clearance issues with the clamp that holds the lid in place? We thought we were able to 'bend' the clamp enough to hold the lid on, it wasn't tight enough to keep the fluid in. During panic stops - the fluid would leak out from under the lid. My husband got some thin (1/8") rubber sheeting that was cut to fit inside the master cylinder lid (above the original rubber liner). This helped keep the lid sealed to prevent leaks.

About 30 Days out...
We've had the brakes for about a month now with a few road miles and trail time. The brakes are AWESOME!!! Our first offroad trip - we were using the ebrake a lot (which is normal on trail rides). The e-brake suddenly stopped working. When we got home - discovered a bolt came out that holds the ebrake cable bracket onto the caliper. Replaced the bolt - and all is good. On the trails.....I can't say enough about how great these brakes are on the trails. THEY HOLD the vehicle on extreme descents and my foot isn't ON THE FLOOR. The true test will be in JULY when we go to Tellico !!

Good Luck with your installation!!!