i installed a ford 8.8 with disc brakes in my xj not to long ago and now im dealing with the brakes not quite being there i have 35" tires and i cant lock them up. i have hear of people using 95 and up jeep boosters and master cylinders? i pulled a zj proportioning valve at the junk yard and i took the spring and plunger out and put it in my jeeps proportioning valve and it just squirted out the nipple? any one running disc brake rear end that good help me out? or who ever knows chime in? thanks

 

Dual diaphram booster will help. Zj prop valve did nothin for me but that could be because i have 3/4 ton brakes front and rear. I also swapped my master cylinder with a newer dodge 1 ton MC that bolted up nearly perfect. But that may be a bit over kill for an 8.8

 

Six Pack, you just need a master cylinder and booster out of pretty much any chrysler vehicle 1990-2000 that had factory 4 wheel disc brakes. The OEM master cylinder in your XJ has that really small rear reservior that was designed to feed the tiny wheel cylinders in the OEM rear drum brakes your XJ came from the factory with. Find a WJ or ZJ Grand Cherokee in your local scrap yard that had factory 4 wheel disc brakes and snag the master cylinder and booster out of it for your XJ. That should work like a champ.

 

when I swapped in a disc 8.8 in my XJ, I gutted the prop valve and swapped in a 78 grand marquis master cyl, braking was improved dramatically. I ran the stock MC for like a day with the discs and it didnt move enough fluid to brake at all, it felt like I had air in the lines but I didnt.

its like $8 for the 78 merc MC

 

for reference:

 

I just did a mc/booster swap into my xj from a 00 WJ. The upgrade is a night and day difference.

The swap took all of 4 hours, and only because ive never made brake lines before.

 

thanks for all the help guys, so i am going to snag booster and master cylinder out of a zj with 4 wheel disc brakes and see how that works in my xj. i will let you guys know how it turns out. dealing with hydraulic brakes kinda sucks since im so use to workin with air brakes haha

 

well i got the booster and master cylinder and prop valve it cost me 25 bucks. the lines are on the other side so i am going to have to buy a double flaring tool off the snap on truck when it comes buy my work. which line out of the master cylinder on the zj master cylinder is for front and which one is for rear brakes?

 

so i have pretty decent brakes that almost lock up 35" do 45 mph it stops in two car lengths, i put the 97 zj v8 mc, booster, and prop valve inners in, didnt have to reem the hole or grind a flat spot on it like it said on naxj to the little aluminum spacer out so the rod was perfect length bent the pinch seem on the fire wall up too make room for the dual diafram booster, adjusted the brake light switch and bought some bubble flared line cut it in half double flared the ends and its all good. great upgrade i was sweating bullets because i read online that the 97 zj booster rods are way too long so i went and bought i 95 booster and mc just in case they all were the exact same length as my 92 xj booster rod they did not have a flat spot on the rod but it didnt matter at all. now im thinkin i want to upgrade my calipers and rotors up front? thanks everyone for the help.

 

So Bo, are we gunna do mine one of these days before we go out? Just let me know when and I'll bring the jeep to work with me.

 

friday? after work?