Swapping drums for discs

[packmule1911]

I was reading in the It's Technical question, a sticky about cheap mods for the XJ. I saw this info:

ZJ - rear discs can be swapped onto a c-clip D35 or corp 8.25

I have an 8.25, and I was wondering about the fine print of putting ZJ discs on. Does anyone here have first hand experience with this modification to their XJ?

[4.3LXJ]

Most people agree that if you have the 8.25, you need to use the Liberty brakes. Those will be a bolt on and use longer cables for the ebrake. Msmoorenburg has done the complete swap.

[drakan1908]

Zjs will work but you need to drill one hole and make the center hole in the back plate slightly larger

sent from a van down by the river

[XJ Wheeler]

Swapped in ZJ discs to mine last year. Love not having to deal with drums anymore. Whenever I was doing research there is a few things no one mentioned.

You need to secure the brake hoses to something, to keep the lines from moving around and getting bent. Since the zj utilizes the coil bracket for this and the xj is leaf in the rear you will have to find another way. I made some brackets out of c channel, welded them to the axle tubes, and bolted them to those. Its a tight space though, and the routing needs to not kink the hose. You also gotta keep clear of the leaf spring ubolt, caliper, and ebrake cable lever.

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You can sort of see it in here, with everything bolted up.

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And because the new setup has a hose, in a new location, the brake lines need to be modded. Now, you can try just bending them to line up and stay out of the way but they're probably original so 14 years of life may cause them to break. No biggie, you can get new line at the parts stores easy, and a bender (may be able to rent one with a refundable deposit). If you need to shorten the line (I did) you'll also need a tubing cutter and flaring tool. But if you've never done this before, try just bending it to use excess line in the bends. Beats battling leaking flare nuts (had that too...).

The stock lug nut studs are too short for the disc setup, so you'll need to pound those out and replace them. You have a few options here. First, you can grab the factory zj studs from the donor axle. But with the chance you could damage the threads upon removal I suggest going with new ones, especially since they're just over a buck each on rock auto. Front xj studs are suppose to be near perfect. Although I have no experience with them, just the zj studs. Here you can see the zj rear stud (left) versus the stock xj rear stud (right).

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The center hole of the caliper bracket does need to enlarged but its very minimal, maybe a millimeter or two overall. I used a combination of a dremel and round file. But a die grinder would be perfect.

The ebrake setup is a bit different on the discs. They use a small drum setup inside the rotor hat. You're in for a lot less work since you have a 97+ also. All you need to do is get new cables. The kj (liberty) cables go right in place of the originals, although the drivers side cable is considerably longer so you'll need to coil it above the axle. Heres a pic of MSmoorenburgs kj cables.

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If you have the pick of the litter of donor axles, go for one with good pads and rotors. I had to replace almost everything (only kept the caliper brackets, lug studs, and brake hoses) to the tune of about $300. And this is an excellent time to replace the rear wheel bearings and seals, should they need it.

Good luck and feel free to ask any more questions. Its a great swap, but I will say a bit more work than most lead on.

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[bluedragon436]

I've been considering doing this swap, quite a bit more since my rear drum setup is shot, and pretty much in need of complete replacement of the drums and shoes for sure... and probably find that the wheel cylinders are leaking if/when I go to do the new shoes and drums...

[myjeep]

what year liberty for this swap?

[XJ Wheeler]

what year liberty for this swap?
I believe the first year had drums but any year after 2002 should have them. Just make sure it has discs and I'm pretty sure they're all the same.

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[Pookapotamus]

What do you think of the greenstuff pads jake?


Having 4WD means getting stuck in more inaccessible places!

[XJ Wheeler]

What do you think of the greenstuff pads jake?


Having 4WD means getting stuck in more inaccessible places!
I'm not really impressed. But to be honest I think I've got some work to do to get the most out of them. I have a dual diaphragm booster and a zj prop valve to go in eventually.

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[bluedragon436]

Been looking at a kit through Rwkhaus (http://www.rwkhaussupply.com/magento/jeep-specific/jeep-xj/jeep-disc-brake-conversion-kit-tj-lj-xj-dana-35-44-and-c8-25.html) or IRO....

[slvmart]

I bought the Teraflex kit, it was $551 when I bought it : http://www.quadratec.com/products/12700_400_07.htm
But you would also need the ebrake cables :
http://www.quadratec.com/products/12700_401.htm
and I ended up swapping a GM disc brake proportioning valve. Amazon.com: 100% Brand New Universal GM Brass Finish Disc/Disc Brake Proportioning Valve: Automotive@@AMEPARAM@@http://ecx.images-amazon.com/images/I/31BC0ltiTnL.@@AMEPARAM@@31BC0ltiTnL

It didn't say anywhere that you need the proportioning valve, but it definitely makes a world of difference. Your standard Proportioning valve is designed to apply pressure (think of it like preloading the rear shoes) to the rear drums at all times. The rear disc proportioning valve applies a much lower pressure to the rear discs. I believe its 10psi with the drums and around 2 for the discs.

The main reason I went this route was that all the components end up being new.

[bluedragon436]

The main reason I went this route was that all the components end up being new.

That is kind of the main reason why I started looking at buying a kit similar to the one I linked above... is due to the knowledge of it all being complete and all being new.... Going to have to redo my front brakes again, as I've been wearing them out quite a bit more then normal, since my back drums are pretty much non existent!!

[XJ Wheeler]

I ended up with mostly new parts for a couple hundred cheaper than that kit but it was a bit of an ordeal to get everything together. The only parts that are reused from the zj axle I pulled are the caliper brackets, brake hoses, and lug nut studs. Probably have $350-400 into it with the 97+ xj/kj ebrake setup, different fluid, and new Timken bearings and seals. But if you can afford it the kit does sound like much less hassle.

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[slvmart]

The Kit really was no hassle, as you stated. It is a direct bolt on. You do need the e-brake cables and nowhere did it state that the proportioning valve would be required. It was just too easy to lock the rear brakes without the correct proportioning valve, and the fronts felt as if they always needed bleeding. At least, in my opinion, it is required.
Now it does stop on a nickel. And if you dislike working on drum brakes (and who doesn't after all these years of discs ?), then it's worth the money (assuming you can afford it).

[bluedragon436]

I ended up with mostly new parts for a couple hundred cheaper than that kit but it was a bit of an ordeal to get everything together. The only parts that are reused from the zj axle I pulled are the caliper brackets, brake hoses, and lug nut studs. Probably have $350-400 into it with the 97+ xj/kj ebrake setup, different fluid, and new Timken bearings and seals. But if you can afford it the kit does sound like much less hassle.

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The Kit really was no hassle, as you stated. It is a direct bolt on. You do need the e-brake cables and nowhere did it state that the proportioning valve would be required. It was just too easy to lock the rear brakes without the correct proportioning valve, and the fronts felt as if they always needed bleeding. At least, in my opinion, it is required.
Now it does stop on a nickel. And if you dislike working on drum brakes (and who doesn't after all these years of discs ?), then it's worth the money (assuming you can afford it).



Oh I definitely hate working on disc brakes, regardless on what type or age of vehicle... I don't know so much if it's that I can afford a kit like the one I listed or if it's the fact of I don't have the time or resources to JY shop and get all the necessary parts to build my own kit out of ZJ or KJ parts... unfortunately my whole 2 JY's are real crappy when it comes to selection of Jeeps for pulling parts, and when they do have ZJ's, they don't keep their rear axles for too long once they get there, the JY usually pulls the axles for sale, and won't let you pull the brake components off of them once they've been pulled from the vehicle... otherwise I would just do that.... not really too worried about the parking brake portion just yet, as I have an auto, and I don't really park on too many hills.. so don't really require the parking brake just yet, but will certainly want to get them working for use on the trails, or while doing repairs if needed..