jeep xj with a rear disc conversion and over sized front calipers. currently has JK axles front rear D30, D44. as of now i am using the stock JK calipers. i havent done any road testing yet since i am still building the engine. my concern is with the rest of the brake system. i know a few guys on here have done axle set ups similar to this. what if anything has been done about the master cyl., per-portioning valve, and the brake booster? my concern is there will not be a large enough volume of fluid moved with the stock XJ brake system. i considered switching it out to a stock JK system, but i havent looked into fitment at all since i quickly realized JKs have ABS and my XJ does not. any input and a little guidance would be much appreciated. also if anyone thinks this thread should be relocated for better results please lemme know. if anyone knows a link to a similar thread please share with me.

 

We need some info. What year XJ? There were different Master Cylinders and Boosters used on different years. One is a single diaphragm booster and the later is a dual diaphragm booster.

 

94 xj country edition

 

Up grade booster to dual with its master be good to go.

 

i will look into that. thanks for the help and the quick response. ive had the same question posted on jeep forum for 2 weeks and no reply. you guys are awesome i will definitely be around more on this site.

 

If that don't help then a hydro booster swap is next,Thats a big job since theres no bolt on options and having custom made power steering lines made for it,But after having one you'll never want vacuum powered brake booster again.The hydro booster stops a lot harder and faster with less foot power.

 

yall dont seem to be concerned about the proportion valve. do i not need to worry about that?

 

Many people do change out the proportioning valve when converting the rear brakes from drums to discs. The guts out of a ZJ prop valve can go right into the XJ prop valve and will adjust the proportioning. I pulled the guts out of a ZJ at the junkyard and popped em right in my XJ when I did my disc brake swap.

With that said, many people never swap it out. You should do it to prevent the rears from locking up early but its not absolutely critical.

 

I also used a ZJ prop valve for my Ford 8.8 disc brakes and it helped with the bias considerably. For whatever reason, the first prop valve I tried made the rear brakes lock up before the fronts, but I got one from a later model ZJ and all was well again (both did have discs and looked identical, maybe I just didn't bleed it properly the first time but they are cheap at the junkyard)

 

I'm running JK44's without issue. I'm even running 6/4 piston Baer big brakes on my stock master cylinder and the braking performance is exceptional. My '01 master cylinder has a 1" piston (which was the recommended size from Baer IIRC), not sure about yours. I am running a ZJ proportioning valve on a non-ABS XJ.



Have you plumed the rear axle lines? Currie sells a great kit for this swap: http://www.currieenterprises.com/CE-6013JK



Elsewhere I'm running XJ brake lines (the front calipers should use the same banjo fittings) and 2-door JK emergency brake cables (I left the mounting tabs on the axle).

 

I do love baer brakes they are made by pbr just like a lot of oem mustang and corvette brakes.And stuff like the pads and rotors are oem stuff easy to replace if need be.

 

The dual diaphragm booster you are looking for will come out of a WJ. I swapped the WJ booster/master into my 90 w/ the ZJ prop valve guts, and an 8.8 w/ discs. Brakes are night and day difference.

 

usn jeep xj, looks like we have the same set up on the front end. i have not done rear lines yet, front is done i will look into the currie kit. i was planning on bending my own but if someone else has done the work its worth a look i may have to make my own any way (rear is trussed). thats a great call on the jk 2 door e brake line i was wondering if it would work. real quick what did you do about speed sensors? i made my own basically spiced xj on one end and jk on the other. havent been able to test yet. i just dont know if the JK uses CAN.
i just checked out that currie link. those are perfect !!!! yall are one step ahead of me now this is great thanks guys!!!!

 

Happy to help! I couldn't find a lot of these answers online when I did the swap and just kind of winged it so I'm more than happy to help someone avoid that headache!

If you're curious about speed sensors I'm assuming you have ABS? The JK wheel speed sensors are part of the CAN BUS system but from my understanding you can just splice the JK sensor into the XJ wiring and it'll work just fine. The XJ PCM does not correlate anything between the wheel speed sensors and the transfercase speedometer sensor so as long as both of your JK axles are from the same year (the tone rings may have changed from '12 to '13), the tone rings will have the same teeth and therefore the antilock computer wont know any different. I don't have ABS on mine but others have swapped JK axles and retained ABS just fine.

I actually used a 2dr e-brake cable for the drivers side and a 4dr cable for the passenger side... the 4dr cable was a little long and I think a 2dr cable should work for both sides just fine. The vehicle side of the JK cable is almost identical to the XJ cables except for an easily removable rubber boot so the factory e-brake assembly can be retained.

 

so this is a classic example you cant see what you're not looking for haha. ive been under that hood more times then i can count and i never even thought to look. i checked the diagram and you are absolutely right about speedo sensor. i got the jeep from a friend of mine who is a grease monkey. i asked him if it had ABS and he said NO. i just took his word for it and never thought about it again. Today though, after your reply made too much sense, my curiosity spiked. i popped the hood and sure enough staring me in the face was a ABS booster pump. in his defense though he was half right. it didnt have ABS, the fuse was blown hahaha. yall have gone over and above i think i have a pretty clear path to follow now. thanks for everything!!!