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Grand Cherokee rear disc brake upgrade


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The swap isn't hard to do. I did the swap from a D35 Grand Cherokee setup to a D44 Wrangler, the hardest part was from having to redrill the hole larger. If you have a D35, it's pretty much a direct swap.

 

The load sensing valve doesn't really care what's on the other side of it but don't think the calipers would like it since it's restricting the flow to them. Most people just flat out remove the load sensing valve, whether they are upgrading to disk or not (I've removed it in both of my MJ's).

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If you do it, get a ZJ proportioning valve and replace the MJ one. You can then dump the second line to the rear brakes. It also gets the rear front bias right for disk rears. If you do a Dana 44 you will have to redrill a couple of the backing plate holes as well as opening up the center hole. Not a big deal.

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In addition to the proportioning valve you will need a few more parts, including:

- New hard/soft lines for the caliper (replacement TJ lines are cheap)

- Disk brake retaining plates (TJ rear disk)

- Longer lug studs (TJ rear disk)

 

I hope to install my ZJ disks to my 44 within the next few weeks before getting the axle rebuilt.

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You'll also need a pair of preload spacers on the D44 (or non c-clip D35). The spacer is required because the ZJ backing plate is not the same thickness as the drum brake backing plate. So to make up the difference and keep the axle seals' preload correct the spacers are required. Otherwise it's leak city. The dimensions for me were .225" thick x by 2.90" OD x 2.45 ID. But you should do your own measurements to be certain. Your favorite local machine shop can fab them up or you can get them from Teraflex for about $6/ea.

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Don please correct me if I am wrong, as it has been a while since I have done my ZJ disc swap research. My understanding was that by using the TJ Rubicon disc brake retainer (and drilling new holes) the pre-load spacer is not required since it is already formed into the retaining plate.

 

The 'lip' on the TJ retainer is almost the same size as the pre-load spacer as seen in this image from naxja.

 

http://farm4.static.flickr.com/3041/285 ... 27.jpg?v=0

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You will also need to figure out the emergency brake cable, the ZJ and MJ levers have different ends. Several solutions. I bought Crown 52" XJ Cables DBC-05 and cut the cable a little shorter. Or you can wrap and clamp the cable around the ZJ end or you can weld the MJ end onto the ZJ lever. And I am sure there are many more.

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