Another Disc brake install

My '01 is slowly evolving, and one of the things I've been planning is disc brakes for the rear. Since I got back from Iraq in May I've installed a RigidCo front bumper, HP D-30 with 4.56 gears and ZJ steering, and 4.56's in the the Chrysler 8.25 to match. I've been watching the yards in the meantime, looking for a ZJ with disc brakes. I found a '95 last weekend and took the backing plates / mounts, calipers, soft lines, and hardware. I didn't have a 12 point 1/4 inch to pull the pin from the carrier so I had to run and get that to finish. Dummy.

It ended up costing me about $58 for the parts :yelclap: The hardware I took included the caliper mount bolts, backing plate mount studs and nuts, and 8 good wheel studs.



From left to right here's the stock XJ wheel stud, disc brake ZJ wheel stud, new replacement ZJ stud, XJ backing plate stud, and ZJ backing plate stud. The nut is just there to keep the new stud from rolling away.



Stock brake assembly:



Axles and brake parts removed:





ZJ backing plate with new parking brake pads. The center bore of the backing plates had to be opened up by approximately .040" to fit over the 8.25 housing. I also had to slightly elongate the mount holes to get a smooth fit. Those junkyard parts cleaned up nice.



Completed assemblies, the brake lines are not hooked up yet though. I ended up flipping the ZJ soft lines from going up from the caliper to down, and I rotated them 180 deg on the mounting surface. This has the soft line mount plate sitting just under the spring pad. I'm going to weld a small tab on there to solidly mount the lines. I just made a loop in the stock lines to take up the extra length. I don't have picture of that yet.





I bought rotors, ceramic pads, parking brake shoes, 4 ZJ wheel studs, and fluids for front and back, including friction modifier for the trac-lok, at Napa for about $180. Since I just had the rear re-geared and the front gears are also fresh it's time for a fluid change, but no need for new bearings and seals in the rear axle. So I'm in for about $240 for my disc brakes so far. I'm thinking of installing Liberty e-brake cables rather than modifying my cables. They're about $40 each at Napa. So no parking brake at this point. I'm going to be installing fresh rotors and pads up front soon. I've been considering the WJ brake mod up front, but we'll see how things work out for a while.

So how do they work? They've only been on there for a day or so, but they feel good! Not as strong as I wanted at first, so I'm trying the Go Jeep proportioning valve mod right now. Seems better, and once I freshen up the front I think it'll be very even front to back.

Doug

Very clean and looks easy enough to do!

Keep it updated

Ron

Yeah, I need to finalize the brake line mounts and hook up the ebrakes. Time (and servicing the front brakes) will tell how much overall improvement there is. Definitely worth it right now though. Not much time involved either, except for JY parts cleaning I think I have about 4 or 5 hours in it. I have to get some pics of the brake line routing, ugly but effective.

Here's something only a Jeep geek would notice!

This looks great.

I'm pulling some zj brakes this weekend from the bone yard. A few questions...
-What special tools are needed for the zj axle? I've done an aussie, but i don't want to go unprepared.
-Did you get the zj studs to work with the xj shafts? I know they need to be longer, Im running moabs also.
-How hard is it to modify the prop valve?

I didn't think you needed to mod the prop valve on the newer XJs....?

JNickel101 said:

I didn't think you needed to mod the prop valve on the newer XJs....?

Click to expand...

yes you definatly do.... well i have a 99, and it definatly needs the prop valve... i dont know about the 00 and 01

JNickel101 said:

I didn't think you needed to mod the prop valve on the newer XJs....?

Click to expand...

Newer XJs have the same proportioning valve as any old one and it "can" (some say "should" or "must" ) be modified when you go to rear discs, as they need more fluid to operate properly.

The thing that changes in the XJ braking system is the brake booster - in the 97 changeover the XJ got a dual diaphragm unit that works much better.

As for the wheel studs - it depends on your wheels. If you have some varieties of aluminum wheels, then yes - the studs arent' long enough. For my stock steelies, I made it over the rotor & through the wheel with plenty of threads showing, no problem.
On the backing plate studs, well, if I could have gotten the old ones out without screwing up the housing I woulda replaced them with something longer BUT it works just fine as is.

i did the same swap on my 01 and i didn't need to change the prop.

CMAHON said:

i did the same swap on my 01 and i didn't need to change the prop.

Click to expand...

lucky you... i need it but cant find one at a yard... well i need to find a yard that will give me just the pvalve. or i could get it from the dealership for 90 bucks

You don't NEED to change the prop valve, but changing it will work better with the discs. And you don't need to change the whole valve, just the internal spring. Try this guy for a used valve: http://www.daveysjeeps.com/

CMAHON said:

i did the same swap on my 01 and i didn't need to change the prop.

Click to expand...

You should try putting the zj prop valve in and see if you feel any improvments... it may seem like you dont need it but I wouldnt be surprised if you saw improvement.

Actually someone on this board went through all the ways of using different prop valves and such and found what you need to change, to have the correct braking feel and max stopping power is to replace the internals of the XJ valve with the spring, internal plunger AND end cap from the ZJ.

I just found the post/pic relating to it.

http://naxja.org/forum/showthread.php?t=978214&page=2

Cool. Really good info here. I hope to do the swap within the next few weeks.

Is it easy to pull the valve? And how much bleeding do you have to do when you change the zj valve?

what did you end up doing about the E brake cables attaching to the ZJ lever things that stick out the back of the backing plate? I'm bout done collecting parts for this but I've seen both the liberty cables you mentioned before and the guys who have chopped the XJ cables and just secured them with a cable anchor type deal.... Otherwise this is a great pictorial on this stuff, and only thing it needs now is a complete parts list for NAPA etc...

I have also read that 2 pass. side Explorer cables work well but haven't seen it in person to confirm. YMMV

Wow, this thread was pretty dead from the start and after four weeks it takes off... LOL.

I'll see if I can answer some of the questions.

No special tools really, but I did get caught out on the 1/4" 12 point bolt retaining the pin in the D-35 carrier. All I had was 6 point 1/4" stuff with me. I already had the calipers off and had to hide 'em while I ran out and got a 12 point box end. :laugh3:

As you can see in the pics the ZJ wheel are studs around 1/4" longer than the XJ studs, I knocked the good ones out of the ZJ axles at the yard then bought a few more. I wouldn't use the XJ studs on this conversion, they're short and it's just to cheap and easy to change.

The proportioning valve is easy to play with except of course you'll have to bleed the brakes again. I was an idiot and forgot to grab the valve off the ZJ when I got the brakes. I did do the go-jeep mod to my proportioning valve after I drove it just once. If you can pressure bleed from the bottom it would be very easy to play with the prop valve and quickly bleed the top of the system.
The brakes work very good, certainly better than before, but the rears do lock up first, but just barely. I'm going to see what she does on the 33/10.50's I'm going to install after I service the front brakes and decide then if I need to fool with it any more.

My Dad has had some health problems so I haven't finished the job yet... I want to weld on a couple of small tabs for my soft line mounts, and I haven't got the e-brake hooked back up. I was going to get some liberty cables and probably will still do that. It's going to be $80 or $90 for both of them, but why not?

I'm really only out the $60 at the yard and the cost of a normal brake job on a ZJ! The $180 I spent at NAPA included all the fluids for both diffs including friction modifier and an extra quart or two.

Parts are easy. At the JY get the backing plates/mounts, calipers including soft lines, whatever hardware you want, and don't forget the proportioning valve! For the hardware try to take the backing plate studs and wheel studs if you can in addition to the obvious caliper hardware. The NAPA parts list is easy too. I just asked for rotors, pads and e-brake shoes for a '94 - "98 ZJ. I'll let you know how the Liberty cables work out when I get them.

Doug

The e brake inside the rear rotor does it have different brake shoes or are they the same??

I didnt need to change the P valve. i did the swap on my '89. Just some common hand tools and some diff and brake fluid. new gasket for your diff as well.

I kept the same studs and I am running Crager Soft 8s.

I took the tightly wrapped coil off of the cables. Looped them around the the links for the emergency brakes and used tiny "u" shaped clamps that I got from Home Depot. They are designed for use one cables and such. People use the clamps on say, a runner cable for their dog, out in the yard. it worked great.

i think i know the answer but i will still ask for clarification. for the prop valve, is there a better year than others? does it have to be the same year as the brakes used? does ABS make a difference.

I don't think it matters what year the prop spring came from as long as it had rear discs and you compare the two and see that the ZJ's is about 1/2" shorter.