Rear disc brake conversion

[mike00xj]

Has anyone done or heard of a disc brake conversion set up that worked well enough to be driven on daily?

2000 xj 8.25 rear

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[Pookapotamus]

I have the terraflex kit on my d44, works great! 5000lbs xj and it stops on a dime! And yes I daily drive mine.


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[drakan1908]

ZJ disc brakes will work. You need to drill some new holes and make the center hole in the backing plate slightly larger. A guy on our local forum did his , if I can find the write-up I'll post a link. Update...here is the link , pictures gone , starts at post 170 on page 17
http://www.vaoffroadsports.com/forum/showthread.php/63-Old-Blue/page17

Sent from a van down by the river

[mike00xj]

ZJ disc brakes will work. You need to drill one hole and make the center hole in the backing plate slightly larger. A guy on our local forum did his , if I can find the write-up I'll post a link. Update...here is the link , pictures gone , starts at post 170
http://www.vaoffroadsports.com/forum/showthread.php/63-Old-Blue/page17

Sent from a van down by the riverAwesome thank you

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[abebehrmann]

Download these extensions for Google Chrome or Firefox and the pics will show up for you.

http://www.xjtalk.com/showthread.php?t=22646

[89limited_hero]

Rear disk brakes from a liberty are a direct swap since it came with a 8.25 with disk brakes from the factory.
http://www.naxja.org/forum/showthread.php?t=977809
http://www.xjtalk.com/showthread.php?t=4961

[XJ Wheeler]

I've done the ZJ disc swap on my 92 with the 8.25 and it's fairly straight forward but more work than any of the write-ups say. And to be honest I would go a different route for mine. If you have plans to swap axles at some point or change gears think about getting a 8.8 that comes with discs, plus you can find them with 4.10 gears. The reason I say this is because I probably spent over $300 on the disc swap alone because of the donor parts needing new pads, rotors, and a few other pieces that added up. I do have a nice new setup but if you can find a donor with good pads, etc I would recommend it more because the cost would be much more appealing. The 8.8 axle swap could cost about the same and now you have better gears and a stronger setup out back. You would still need to change the front gears but once you add the amount you save on rear gears it makes sense. I just have to add that disclaimer now that I learn more, your choice of course.

I went with the ZJ disc swap instead of the Liberty discs because my local junkyard had a dozen ZJs to choose from but only one Liberty that wasn't missing pieces so if you can find a Liberty donor I wouldn't hesitate to grab those. Only notable difference is you will need to open up the center hole of the ZJ rotors just a tad to fit onto the axle, whereas the Liberty is already set to it.

Things you'll need to grab from the donor...
-rotors
-pads
-backing plates/caliper brackets
-calipers
-soft brake lines
-lug studs
-ebrake cables (from a Liberty)

A few things that usually don't make the write-ups.

You'll need to re-bend your brake lines, however you're dealing with 17 year old lines that don't want to change shape so you may end up needing to bend up some new ones. This is easy if you've never done it.

The soft brake hoses need a base to mount to where they connect to the hard line. This is to keep the constant movement from stressing the line and cracking it over time. I made a small bracket per side similar to a perch like for the leaf spring and welded it to the axle tube between the leaf spring and backing plate. If you don't want to/have access to weld I think you may be able to make a bracket to bolt to the shock mount, or sway bar mount if yours has one.

Your jeep is a 97-01 meaning it's super easy to get the ebrake working again. You just need to grab a set of cables from a Liberty. They will work with either setup too.

The lug studs need to be swapped out as well. The stock drum studs are too short to engage enough threads. You have a few options here. You can get the donor lug studs from either the ZJ or Liberty. I used the ZJ ones on mine. You can also use front XJ studs as well. If I did it again I would go with new XJ front studs just so everything matches and I could substitute one from the rear in case a few of the front broke, or vice versa.

All in all its worth it, even having the added cost of replacing the maintenence parts I did. And if you want to keep the 8.25 and stock gears don't second guess it. I love not having drums anymore and don't ever want to go back. I don't daily drive mine but that's just because we have a 1 ton we drive for work. It's basically like it came from the factory like that.

Hope this helps!




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[mike00xj]

I've done the ZJ disc swap on my 92 with the 8.25 and it's fairly straight forward but more work than any of the write-ups say. And to be honest I would go a different route for mine. If you have plans to swap axles at some point or change gears think about getting a 8.8 that comes with discs, plus you can find them with 4.10 gears. The reason I say this is because I probably spent over $300 on the disc swap alone because of the donor parts needing new pads, rotors, and a few other pieces that added up. I do have a nice new setup but if you can find a donor with good pads, etc I would recommend it more because the cost would be much more appealing. The 8.8 axle swap could cost about the same and now you have better gears and a stronger setup out back. You would still need to change the front gears but once you add the amount you save on rear gears it makes sense. I just have to add that disclaimer now that I learn more, your choice of course.

I went with the ZJ disc swap instead of the Liberty discs because my local junkyard had a dozen ZJs to choose from but only one Liberty that wasn't missing pieces so if you can find a Liberty donor I wouldn't hesitate to grab those. Only notable difference is you will need to open up the center hole of the ZJ rotors just a tad to fit onto the axle, whereas the Liberty is already set to it.

Things you'll need to grab from the donor...
-rotors
-pads
-backing plates/caliper brackets
-calipers
-soft brake lines
-lug studs
-ebrake cables (from a Liberty)

A few things that usually don't make the write-ups.

You'll need to re-bend your brake lines, however you're dealing with 17 year old lines that don't want to change shape so you may end up needing to bend up some new ones. This is easy if you've never done it.

The soft brake hoses need a base to mount to where they connect to the hard line. This is to keep the constant movement from stressing the line and cracking it over time. I made a small bracket per side similar to a perch like for the leaf spring and welded it to the axle tube between the leaf spring and backing plate. If you don't want to/have access to weld I think you may be able to make a bracket to bolt to the shock mount, or sway bar mount if yours has one.

Your jeep is a 97-01 meaning it's super easy to get the ebrake working again. You just need to grab a set of cables from a Liberty. They will work with either setup too.

The lug studs need to be swapped out as well. The stock drum studs are too short to engage enough threads. You have a few options here. You can get the donor lug studs from either the ZJ or Liberty. I used the ZJ ones on mine. You can also use front XJ studs as well. If I did it again I would go with new XJ front studs just so everything matches and I could substitute one from the rear in case a few of the front broke, or vice versa.

All in all its worth it, even having the added cost of replacing the maintenence parts I did. And if you want to keep the 8.25 and stock gears don't second guess it. I love not having drums anymore and don't ever want to go back. I don't daily drive mine but that's just because we have a 1 ton we drive for work. It's basically like it came from the factory like that.

Hope this helps!




Sent via messenger pigeon. I talk, he types.Thank you for all of the info!

You said the 8.8 swap would be about the same price. And I've seen a few guys do it. What would be the pros/cons?

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[4.3LXJ]

Pros is a much stronger axle, unless you already have the 29 spline axles on the 8.25. Then you would gain some. Cons are that you need to weld in spring pads and get a U joint adapter for the pinion flange

[mike00xj]

Pros is a much stronger axle, unless you already have the 29 spline axles on the 8.25. Then you would gain some. Cons are that you need to weld in spring pads and get a U joint adapter for the pinion flangeI'm not sure if I have 27 or 29 yet. Thank you for the info though!

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[89limited_hero]

29 spline you have all 97+ xjs came stock in the 8.25. Unless for some crazy reason someone before swapped in an older 8.25 early 90's- some 96s. Were 27 spline.

[mike00xj]

29 spline you have all 97+ xjs came stock in the 8.25. Unless for some crazy reason someone before swapped in an older 8.25 early 90's- some 96s. Were 27 spline.That's great to know. Thank you!

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[XJ Wheeler]

Yeah, I forgot to mention the 8.8 does require welding. For that install you would need to weld on new spring perches and shock mounts, get a new yoke or adapter, new ubolts, possibly be able to use the ford ubolts plates, and depending on your wheel setup wheel spacers because the 8.8 is slightly narrower. Just got through doing this swap on my brothers '90.

A quick rundown comes up right at $300. My local junkyard has rear axles for about $100. That varies greatly though and of course makes all the difference. But axle-$100, ubolt-plates-perches-shock mount kit-$140, yoke adapter-$40. Just add some paint, welding wire, etc and you're done.

Another possible plus if yours doesn't have the limited slip is some 8.8s did come with a lsd. It is harder to find a disc, 4:10, lsd axle though.

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[bluedragon436]

Can't wait to upgrade my rear brakes from drums... I just replaced all of the parts @ the wheels for the front and rear brakes, with the exception of the lines. And it stops far better than it did when I first got it.. but definitely not to where I feel it should be...

[denverd1]

8.8 cons: swapping axles seems like a lot of work for marginally deeper gears and disc brakes. then you need gear set for the D30 and need to know how to setup gears. I wouldn't swap an axle to get disc brakes/4.10s.

[bluedragon436]

8.8 cons: swapping axles seems like a lot of work for marginally deeper gears and disc brakes. then you need gear set for the D30 and need to know how to setup gears. I wouldn't swap an axle to get disc brakes/4.10s.

Yeah that is kind where I was when it came to doing my regear... I had thought about doing the 8.8... but wasn't worth it to me, since I have the 29spline 8.25.. Now I just got to get the disc upgrade going.. and eventually doing the front WJ brakes..

[XJ Wheeler]

8.8 cons: swapping axles seems like a lot of work for marginally deeper gears and disc brakes. then you need gear set for the D30 and need to know how to setup gears. I wouldn't swap an axle to get disc brakes/4.10s.
I just have the 27 spline 8.25 so it's another plus for me.

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[denverd1]

I just have the 27 spline 8.25 so it's another plus for me.

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still a marginal improvement. but to each their own. then you gotta regear the front. can you setup gears?

[abebehrmann]

still a marginal improvement. but to each their own. then you gotta regear the front. can you setup gears?


I don't have the book in front of me, but Eric Zappe's book has a chart of the strength of each axle and I remember being surprised at how much stronger the 8.8 is than even the 29 spline 8.25.

[denverd1]

I don't have the book in front of me, but Eric Zappe's book has a chart of the strength of each axle and I remember being surprised at how much stronger the 8.8 is than even the 29 spline 8.25.

comparable to a 44 IIRC. What tires are going on to match this awesome axle upgrade? could handle 35's, but we've got 4.10s.. see what I mean?

looks like you'll also need DS customized and have a narrower stance than 27 spl 8.25.

[XJ Wheeler]

still a marginal improvement. but to each their own. then you gotta regear the front. can you setup gears?
Sorry for the late reply.

My brother's getting the tools together to do his and we're gonna learn to set them up together. Plus I'm planning to regear either way. I do think going 4.56 would be a better idea and the 8.8 doesn't come with those so I may just build up the 8.25 since I've already got the brakes and cover. Decisions...

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[jnelson101]

I was about to do a conversion to disc from a liberty but as I was looking over the assembly/backing plates I didnt see anywhere to mount the speed sensor for my abs. My 2000 has a has a hole where it clips in. How is that handled without having a constant abs light on? BTW.... Yes Im sure its something very apparent that I am not thinking about!

[89limited_hero]

Well the liberty is an 8.25 and you have a dana 35.
You need the grand Cherokee dana 35 set up.
The reason for this is 8.25 didn't come with asb and the dana 35 did. You won't find a cherokee with an 8.25 with abs. With the grand Cherokee/zj had abs dana 35 and disk brakes and will be a bolt in job for you.

[prerunner1982]

@jnelson The Liberty's rear vehicle speed sensor is in the differential. It appears the ZJ Grand Cherokee offers the rear disk components with the VSS in the backing plate and appears the conversion is pretty much bolt on though it may require the ZJ VSS to be spliced into your existing wiring.

[jnelson101]

Ok that makes sense now so with my setup its probably best to go with a zj setup. I wish I had asked before because I didnt even look at any ZJ's since I could get newer liberty parts. The local LKQ pick your part junkyard had black Friday sales last weekend with 40% off. I could have picked that stuff up cheap!

[prerunner1982]

Sell what you have to someone with an 8.25 looking to upgrade.

[bluedragon436]

Yeah.... now if only we could find someone with a 8.25 that'd take that Liberty disc conversion off your hands to help fund the ZJ parts...... OH wait... I'd take em off your hands depending on what all you had, how much you'd want for em and shipping... lol I'm sure there are quite a few others that would take em off your hands as well, to help fund your ZJ parts purchases...