Rear Disc Brakes on Chrysler 8.25 Rear Axle
I finally got tired of dealing with drum brakes…..so I decided to do something about it. By installing ZJ rear disc brakes on my XJ. I know there are a few write-ups out there already about this conversion, but figured I’d make this one since I know it will be around for a while 😉
First thing you need to do, is acquire the rear disc brakes off of a ZJ. I managed to score a set on eBay for a pretty decent price, but you can also check your local salvage yard as well.
I managed to get everything I needed in one shot. Here is what you are going to need:
– 2 Caliper Brackets
– 2 Backing Plates (Only needed if you want to retain an e-brake)
– 2 Calipers (Mine were in good shape, otherwise you can get new ones from an auto part store)
– 2 Rotors (I had the ones I got cut with no problems)
– Set of Brake Pads (I went out and got new ones)
I also managed to get all the bolts and e-brake cables. I did need to have the rotors turned, but then they were as good as new (you can also see my new pads in the picture).
Once you have everything that you need, it’s time to start the install. The first step here is to jack up the rear end, remove the wheels, and get those old drums off.
Now you need to remove the differential cover and drain the gear oil. Next you need to remove the bolt holding the cross pin in the carrier (it’s 5/16″)
Then you can remove the cross pin as well
Now the axle shafts need to come out. All you need to do is push in each axle shaft until the c-clip falls out and the shafts will slide right out. Don’t lose the c-clips!
Then go ahead and remove the four bolts holding on the drum backing plates so you are left with only this:
If you need or want to replace your wheel bearings, now would be a great time to do that. I decided to skip that this time. Next I bent the hard brake line where I wanted it, and connected the new soft line to it. I routed it right now so that it comes up and then down again before connecting to the caliper. This will help keep it from getting snagged on the trails. I have not mounted the line yet, but plan to make a mount that will bolt to the leaf spring plate in the future. You can see the soft line in this picture:
Now comes the only modification that you need to make for this conversion to work. You need to enlarge the center holes of the caliper bracket and backing plate, and drill out the bolt holes just a little bit. I used a die grinder on the center hole and just a normal drill on the bolt holes. The modification is very simple, as not much material needs to be removed for it to fit.
Now you can go ahead and bolt up the caliper bracket. I used the nuts that came off of the ZJ to mount it to the axle.
Then you can reinstall the axle shafts:
Load up the calipers with the new pads:
Finally, install the rotors. Don’t forget to bleed your brakes.
Put your wheels back on, and take it out for a test drive. You should notice an increase in braking performance.
I have not done anything with the e-brake yet, but I do plan to in the future. When I do, I will add another tech article showing how I do it.