JRusty15

First, yes, I have searched and read through many of the articles, how-to's, videos, etc on how to upgrade the drum brakes on my XJ in the rear to disc brakes from a ZJ. I understand the basic principles, and as a hobbyist mechanic, I feel comfortable enough tackling the job. Plus it's a good excuse to replace the rear diff fluid!

In any case, I just wanted to put this post out there to see if there are any specific things to consider for my swap. I have a '99 XJ and I'm not sure how to tell which rear-end I have. I just recently replaced the proportioning valve as I stripped some of the threads, but I didn't realize that I should be using the ZJ proportioning valve, so I ordered one for the XJ. Will it be ok just using the XJ one? Or should I replace the spring? Also I saw a video where someone was doing this swap on an '89 and had to shim the backing plates to put load on the axles. I didn't quite understand that, but wanted to know if that's something I had to do on mine? Also will I need to replace the wheel studs with longer ones? I saw a few people mention that, but if I need to I wasn't sure where to get the studs. Can I pull them from the ZJ? My local junkyard has like 11 ZJ's so I should be able to grab all the parts this weekend.

And if there are any other details to consider, or things to keep in mind, things you guys may have had trouble with or whatever, please post and let me know.

Thanks! This community has been great so far!!!

WyoCherokee

Because you did not mention ABS, and i would assume 4.0, AW4, you should assume a Chry 8.25. BY doing the ZJ upgrade, you will need everything off the ZJ from the backing plate bolts all the way out to the calipers and wheel studs. The backing plate will not fit over the Chry 8.25 Hub Case without some massaging from a dremel tool on the backing plate it self. Clean up the Hub Case with a wire wheel and flap disc and give it a clean shot of paint before installing the backing plate. Yes you can use the XJ block, but the ZJ block would be preferred.

JRusty15

Sorry for not mentioning more details, but yes, there is no ABS and its the 4.0. Opening up the backing plate to fit is not a problem. I just wanted to make sure I didn't have to worry about anything else regarding the axles in the rear-end. Thanks!

SolerXJ

Check this out:

https://www.cherokeeforum.com/f51/re...-8-25-a-57807/

JRusty15

Thanks! I did see this post. I just wasn't sure if this was the same rear-end that I have, but looks like it is. Thank you!

investinwaffles

I just did the swap (yesterday)

Grab the following parts;

- Backing plates and parking brake hardware from a ZJ
- Calipers from the ZJ (don't forget the caliper mounting bolts)
- Proportioning valve for ZJ (Don't skip this, it helps distribute more pressure to the rears for more even brake bias)
- Brake hoses closest to the caliper


Buy new;
- Brake pads
- Rotors (Napa Premium rotors are only $30 each)
- New brake slider boots if your brake pads don't come with them (mine apparently did so I have an extra set)
- Grade 8 backing plate bolts (3/8"-16 1.25" bolts, nuts, and lock washers)
- ZJ Wheel studs (DORMAN 610234)
- ALL NEW lug nuts for your new wheel studs (good idea if your lug nuts ere as thrashed as mine). I went with these;
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

- These e-brake cables;
http://www.morris4x4center.com/rough...-5-dbc-06.html
http://www.morris4x4center.com/rough...25-dbc-07.html

- Diff fluid (AMSOil 75w90 severe gear is excellent)
- Also do the rear wheel bearings and seals at the same time. Took me an additional 10 mins per side


Buy all of the stuff online as cheap as you can to help offset the cost, and make sure you have everything you need before getting started.


Basic steps;
1. Remove wheels
2. Remove diff cover, drain differential
3. Remove axles
4. Remove backing plates and entire drum assembly (unscrew brake lines, leave the parking brake cable attached and just set the drum assembly aside)
5. Remove backing plate studs with a hammer (they come out pretty easily)
6. Remove wheel studs with a hammer (use a block of wood under it)
7. Press or smash wheel studs back in (I used 2 blocks of wood, and just hammered them in with some lubricant to assist, went in easy)
8. Grind backing plate to fit axle tube
9. Mock up rotor and caliper, bend brake lines to match ZJ brake hoses
10. Install parking brake cables (I just cut my stock ones at the equalizer bracket to save the hassle)
11. Bolt up the brake caliper and rotor, make sure the axle turns smoothly
12. Adjust parking brakes
13. Install and Bleed proportioning valve
14. Bleed brakes
15. Put wheels back on and bed in brake pads

redmuck

are those plastic master cylinders dual chamber? like my steel one, separated, one for the back, other for the front. where one blows, you still have somewhat brakes.

cruiser54

Very nice write-up!!
I would like to add though, that it's way easier to just swap the prop valve guts, and cheaper to acquire.

WyoCherokee

Good List. Sticky Material

JRusty15

Yea thanks for the information! That was great! Unfortunately those links are giving me 404 errors :-(

Regardless I'll be heading to the junkyard this weekend to pick out all the ZJ parts I need!

investinwaffles

That is strange, I will post up the part numbers when I get home later.

And as far as the prop valve goes, you just need the guts (cap, spring, and valve thingy)

​Check out this video for the full install (worth watching a few times through)

​​​https://youtube.com/watch?v=fwi2g40ymL0

JRusty15

I was able to get to the junkyard over the weekend. We only found about 4 ZJ's in the yard. Two of which were not accessible, one was SUPER rusty in the back, and the 4th one was decent enough for us to salvage parts from. We got the proportioning valve which looks in perfect shape. The rear was fairly rusty, so we only took the backing plates. The calipers were dry, cracked and rotted, and everything else I can pretty much buy new. We had a hell of a time getting the axles out because of limited access space, but we were out of there in about 90 minutes all said and done.

Next step is to order all the new parts and get these backing plates cleaned up.

JRusty15

Sorry, just had a quick question as it came to my mind. Can I re-use the parking brake parts on my XJ? I haven't removed the drums yet and don't know what's there. And I noticed in the post above that investinwaffles didn't mention parking brake parts. Thanks!

Cane

you can buy small clamps and loop the end of the parking brake in order to secure it into the parking brake lever thingy. not sure about different years and different lengths, but i heard it's an alternative.

JRusty15

I spent yesterday preparing the back for the new ZJ brakes. All of the new parts are in the mail and set to arrive later this week. So I popped out the axles, removed all the drum brake equipment, popped out the wheel studs (new ZJ length ones incoming), and replaced the bolts that held on the backing plate with new grade 8 bolts.

Unfortunately when trying to remove the hard brake lines from the drum backing plate, the line turned with the nut and broke off....on both sides! Luckily I have a spool of brake line and some connectors as I originally had intentions of replacing all the rusted out lines. This should making connecting the disc brakes much easier.

Lastly, I don't think I have the dust shield plate that goes between the parking brake assembly and the ZJ bracket for the calipers. Do I need that part? Or can I get away without it? The ones from the donor car were in terrible shape so I didn't take them.