rear disc brake conversion question

Is there anyone that has done the conversion and wish they didn't? Is there any hidden problems that you came upon that I should know about? Anything that I should buy before I start? I'm asking because I will have one day to take the brakes off of the ZJ and put them onto my Cherokee.

My ZJ discs work great.

You will have to open up the hole if you are bolting them on a 8.25 or a XJ D44. Not much though.

If its going on a XJ D44 you will have to get TJ D44 bearing retainers and redrill the mounting holes.

You'll have to do something about the Ebrake cable and obviously the brake lines. Otherwise, im happy with the swap, and the Jeep stops ALOT better, even with the stock MC, booster, and prop valve.

The one issue that I had was not knowing exactly what year I was picking crown vic parts from .... I knew I wanted mid 90s Crown Vic.... I thought I had a 94 cv and got the new calipers for it... turns out they did not match... but the 97's did. It was a couple of extra trips to the parts store.

This was not in any way the fault of the swap... I just that I did not know my cvs well enough to tell a 97 from a 94 once they were gutted at the JY.

The other issue that I am working on now is that the face of the rotor is thicker than the drum... and thus moves the wheel mounting service out like 1/4 inch. This makes the snout on the axle shaft look a little short... I am running stock axle shafts in my D44 and I might have to upgrade to alloy shafts to get a longer snout no the axle shaft.

The axle is not yet under the jeep so I am not sure about it yet.

I'll be doing the swap on an 8.25, sorry

CanMan said:

My ZJ discs work great.

If its going on a XJ D44 you will have to get TJ D44 bearing retainers and redrill the mounting holes.

You'll have to do something about the Ebrake cable and obviously the brake lines. Otherwise, im happy with the swap, and the Jeep stops ALOT better, even with the stock MC, booster, and prop valve.

Click to expand...

For the D44.. TeraFlex makes the spacer You can then keep your stock retainer and not have to re-drill TJ spacer... the Explorer thread has the PN. They also make the soft lines to match up with the Ford calipers and Jeep Hard lines.

With the TeraFlex soft lines on the '97 CV calipers I just had to use the CV banjo bolt instead of the TeraFlex one... The threads were a different pitch.

Semper Fi said:

I'll be doing the swap on an 8.25, sorry

Click to expand...

Just gotta grind out the center a bit then. The rest is cake.

ask asp387, he just did the swap this past weekend onto his 8.25

JAS said:

For the D44.. TeraFlex makes the spacer You can then keep your stock retainer and not have to re-drill TJ spacer... the Explorer thread has the PN. They also make the soft lines to match up with the Ford calipers and Jeep Hard lines.

With the TeraFlex soft lines on the '97 CV calipers I just had to use the CV banjo bolt instead of the TeraFlex one... The threads were a different pitch.

Click to expand...

IF he had an XJ D44, and still was going to use the ZJ Grand Cherokee discs brakes, he would still have to redrill the caliper mounting bracket.

I didnt know Teraflex made a spacer, might be something to look into for future swaps we do.

I did it on my 8.25 with ZJ parts - here are my notes...
First off, grinding out the center hole? Do yourself a favor. Buy a rotary burr or something, ANYTHING but a die grinder or dremel. The backing plates are 3/8 steel or something stupid and it took me a while to get them opened up enough, lots of test fitting and a few broken grinding stones. Not impossible with lighter tools, but I wish I'd had something with more "oomph".
Second - I don't know how common this is since I'd never heard of it before - but I had to drill out the four bolt holes that hold the backing plate to the axle housing. I don't recall how much, but I think it took three stages of drilling (stepping up the bit size slowly) over four holes on two sides before I could get the damn things to line up & fit onto the axle.
Third - I used one ZJ cable (drivers, I think) and one XJ cable (passenger's, highly modified). This part nearly broke my heart - it was a pain in the ass and due to my issues with manual dexterity added to the stiffness of the inner cable (once you get through the plastic & steel sheathing) resulted in some bleeding knuckles as well. Do yourself another favor - buy the Jeep Liberty cables. I'm almost always broke (don't ask) and so did it on the cheap, but damn - woulda been easier with KJ cables.
Other than that - lets see..
Rear discs require more fluid volume to work properly than drums. With the pressure being spread thinner, my failing master cylinder became a lot more apparent. I didn't realize I had a problem there but I'm now pretty sure of it. Oh well - time to go WJ MC / Booster.
I'm pretty darn happy with the swap though - I'm even looking at wheels to show off the discs better. Of course only jeep dorks would even notice...

i didn't have to drill holes to get everything to line up, i did forget how much of a pain the backing plates were though, already. i used a pneumatic die grinder but it was indeed painfully slow.

do KJ cables have the square eye that ZJs use? i ended up making some funky brackets using some parts from the xj drums... it worked for a bit then one of them popped off. i'm goign to have to do something about that.

I cut back about 5" of sheathing (very slow. Thank god for safety goggles - semi-molten plastic & bits of steel flying as I used a rotary tool to cut...) on the parking brake cables and two cable clamps to form a tight loop & hooked that over the actuator arm on the parking brake assembly. Might be "ghetto" but it works & hasn't caused me any grief.
Yeah, I don't know what was up with having to drill - but I couldn't get the thing to fit without enlarging the mounting holes by 1/16" or so. Drilled it all out & it fit like a glove - thought I barely needed to put the nuts on it.
KJ parts have the square eyes, yes. Only issue is length, but that can be solved by zip-tying everything up out of the way.

The dremel worked fine for me to open it up took about 5 mins each side. I also had to drill out the bolt holes on the backing plate. and if your replacing the wheel bearings do not buy the one that has the bearings and wheel seal all in one package. buy them separate. Make sure you have all the parts the first time. I am still happy I did it. I was having to fix the drums about every third time I went wheeling.

go ahead and buy new ZJ studs to put on your axles, they're slightly longer to take up the added thickness of the backing plates...........the xj studs just didn't leave enough threads left

i used the factory ebrake cables and a single chain link to hook up my ebrakes (loop it around the arm and put the cable end through the other side of the link, tighten everything up), simple and works terrifically

yossarian19 said:

KJ parts have the square eyes, yes. Only issue is length, but that can be solved by zip-tying everything up out of the way.

Click to expand...

are they super excessively long? 5-6 ft? i think they are... if that's the case, that's fine because i'm running 2 stock passenger side xj ebrake lines right now because the stock xj driver's side one was um... a bit tight.

Fred85 said:

go ahead and buy new ZJ studs to put on your axles, they're slightly longer to take up the added thickness of the backing plates...........the xj studs just didn't leave enough threads left

Click to expand...

I left the specialty parts at the stealership. Bought some 5/16" or 3/8"(whatever size they were) grade 8 bolts, washers, and nyloc nuts.

x2 on the rotary burr. $14 from mccmaster carr, no dicking around w/ a dremel....

my only regret is the loss of the ebrake, i couldnt be bothered...

CanMan said:

IF he had an XJ D44, and still was going to use the ZJ Grand Cherokee discs brakes, he would still have to redrill the caliper mounting bracket.

I didnt know Teraflex made a spacer, might be something to look into for future swaps we do.

Click to expand...

Yea... the Teraflex part number is in the Explorer thread

http://www.naxja.org/forum/showthread.php?t=967146&highlight=crown+vic

This is the teraflex catalog with the partnumber on pages 92

http://www.teraflex.biz/wp-content/uploads/catalog/TeraFlex_2008_catalog_web.pdf

xcm said:

x2 on the rotary burr. $14 from mccmaster carr, no dicking around w/ a dremel....

my only regret is the loss of the ebrake, i couldnt be bothered...

Click to expand...

just put a line lock in

Thanks for all the help guys, I'll let you know how it goes. I plan on doing the swap this coming Wednesday

256offroad said:

just put a line lock in

Click to expand...

Not good.

It has been my experience that "line lock" or "park lock" devices leak down over night. Luckily, I found this out while living in flat Florida...