Well I'll be...a tech write-up! Will have pics downloaded later.
Affordable C-Clip Dana 35 disk brake swap
My buddy was having issues with his drum brakes on his 91 YJ and was overall not happy with the performance of his braking system since putting the rig on 33s. He decided he wanted to do a rear disk brake swap. So we started looking at options.
He wanted to retain his parking brake, so that ruled out a homebrew setup. The first thing that comes to mind for many is to swap the Dana 35 out for a Ford 8.8 for the stronger 30 spline axles and disk brakes. This was not an option in his case because he already had a 30 spline “super 44” kit installed with an ox-locker. Aftermarket kits run in the neighborhood of $600, so that was out. So we decided to swap the disk brakes from a Grand Cherokee. So we set out for the pick-a-part and found a 93 Grand Cherokee with a c-clip Dana 35 for a donor.
Things you will need from your donor-
Calipers w/ brake hoses
Rotors*
Backing plates w/ park brake hardware
Parking brake cables
Proportioning valve (optional)
Brake hard-lines (optional)
*I suggest actually picking up new rotors. We took the rotors because they looked ok and thought we would save a few bucks over new. Unfortunately the ZJ rotors do not have much difference in thickness between new and minimum thickness, so the rotors we picked up could not be turned. Also, the rotors cost $20/ea at the junkyard, and were $25/ea new at the auto parts store.
Note: The ZJ has a center mounted parking brake handle, while my friend’s YJ had a foot parking pedal. This means that the ZJ passenger side parking brake cable will be too short to meet the parking brake connections driver frame rail of the YJ. We ended up pulling a passenger side park brake cable from a disk brake explorer, which worked perfectly. A TJ or XJ may be able to use both ZJ brake cables as-is.
Money saving tip- If you pick up the explorer cable at the same time as your backing plates, pull the ZJ cable off and leave it behind, and install the explorer cable. This way you don’t have to pay for the extra cable.
Disassembling your donor-
Disconnect the brake hard lines from the brake hoses at the calipers. Remove the bolts holding the brake hose tabs to the axle. Remove the two bolts holding each caliper and remove the calipers. Remove the rotors (you may need to back off park brake adjuster). Remove the diff cover. Using a 12 point 1/4” box end wrench remove the cross pin bolt. Remove the cross pin from the carrier. One at a time, push the axles in and remove the c-clip, then remove the axle from the housing. Disconnect the parking brake cables from the adjuster and bracket under the center of the body. Remove the abs sensors from the back of the backing plates. Remove the four nuts holding on each backing plate. Remove the backing plates (you may need to use a hammer and punch and drive the four studs out of the axle flange before pulling the backing plate). Pull the brake hard lines from the junction block on the axle (optional…we left these behind, and the YJ lines worked fine after re-bending them to meet the brake hoses). Remove the brake proportioning valve from beneath the master cylinder (optional).
Install-
Disassembling your rig is the same as it was for your donor (assuming you have a c-clip axle), except replace the word “rotor” with “drum”, and replace the word “caliper” with “drink a beer”.Don’t remove your brake hard lines unless you are replacing them with the ZJ lines. Also if you have a locker (as was the case here), you will probably have different methods for removing the c-clips. In our case the ox locker has a cap you remove from the side of the carrier and then you fish the spider gear through a hole that is about .050” too small for the gear. The trick to get it out is to stick your tongue out to the left and wiggle your right toe in a circle while removing the gear.
Now would be a good time to install new axle seals in needed.
PAY ATTENTION THIS IS VERY IMPORTANT!!
While you have your axle shafts out place a rotor on the axle shaft and then place the axle in the wheel like you are putting the tire back on. MAKE SURE YOU HAVE ENOUGH THREADS FOR PROPER LUG NUT TIGHTENING. The rotors are thicker than the original drums, and if you have aftermarket wheels you may find your studs are too short. We found this out the hard way after completely re-assembling the axle. Try finding aftermarket screw-in studs on a Sunday.
Now, install the backing plates to the axle. Slide your axle shafts in one at a time and install the c-clips. Reassemble your carrier cross pin (make sure the thrust washers under the spider gears are installed properly). Install the rear cover and add gear oil. Install the rotors. We replaced both the rotors and the pads with new. Install the calipers.
For the brake lines, we ended up straightening the factory lines and then re-bending them to meet the ZJ brake hoses. The ZJ brake hose has a mounting tab built in which may/may not be convenient for attaching to a homemade tab on the axle housing. You may want to consider finding an alternative brake hoses that will fit in a standard tab with a spring clip. For now we used a heavy duty zip tie to secure the hard line to the axle housing until we get around to making/welding on a new mounting tab. After connected bleed the brakes.
For the park brake cables we found that the passenger side needed to be routed to the top of the pumpkin (zip tie to brake hard line) and then between the drivers side shock and the track bar mount to get to the frame rail cable mounting bracket. The driver’s side cable made a semi loop in front of the shock and then proceeded to the mounting bracket. We found that the factory YJ park brake splitter/linkage had to be extended to get it to reach the new park brake cables. We did this by cutting the threaded adjuster rod near the eye end and threading a steel turnbuckle with jam nuts between the two halves.
Don’t forget to re-adjust your parking brake adjusters at the backing plate.
Researching on the internet we found a variety of ways that people have dealt with the proportioning valve. We decided to leave the original valve in stock form and come back to it later if the brakes don’t feel like they are performing well enough. If he feels like they don’t brake enough we will swap in the ZJ proportioning valve.
Cost-
Calipers, loaded backing plates, and rotors from junkyard - $134
New rotors, pads, axle seals, misc fluids/cleaners - $88
Total- about $180 (not counting the j-yard rotors)
After a quick road test we noticed improved braking and a more effective parking brake over the original drums. He should also see much less loss of braking power when in mud/water as is typical with drum brakes. Overall, besides the headaches, we feel this swap was worth it.
Reply With Quote
Originally Posted by Graystroke
