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Brake booster/MC swap

MoabXJeeper

MoabXJeeper

NAXJA Member #1398
Location
Salt Lake
I need some help on a new brake booster swap (and sorry I suck at searching, I'm sure this question has been asked many times before).

I've got a 92 Cherokee on 35's running the stock booster that's been in there forever and I'm getting really sick of mediocre brakes. I picked up a newer model booster (96+) and plan to drop it in to hopefully increase some braking power.

I should also mention I have a Ford 8.8 in the rear with disc brakes (that I don't think really do anything right now).

1. Will this be a drop in replacement for my current booster?

2. Will I need to buy extra brake lines since the MC is a little different?

3. I've heard of needing a new proportioning valve, is that an absolute necessity for running disc brakes?

Anyone that can chime in and even offer any hints, I would really appreciate!
 
Should swap right onto a '92.

I was able to reuse one line when I did the swap on my '92 MJ, but I had to bend and flare one new one.

It has been suggested to take the internals out of a ZJ prop valve and swap them over, I did this on my '98 that I converted to discs and didn't notice a difference.
 
Moab, the booster swap will be a noticeable improvement, but with 35's, you will only see a significant braking improvement by installing larger rotors/calipers. A WJ brake swap is one of the best improvements that I have done to my rig, or any of my previous XJ's.

The added benefit is improved steering/handling.

Here's my write-up; there are many others WJ swaps documented on NAXJA.

http://naxja.org/forum/showthread.php?t=913774&page=9

I'm also going to go out on a limb here and declare the best way to fine tune your front to rear brake bias after performing a rear disc/larger front disc swap is to install an adjustable brake proportioning valve.
 
I'm also in the same boat as you. I will be doing the WJ swap eventually, but the single diaphragm in my 93 just doesn't cut it.
 
Thanks for the response guys, it's much appreciated!

So a little update, I got the old booster out last night.



I need some suggestions now. I know a Grand Cherokee proportioning valve would be the preferred way to go, but I don't really know where to find one and I'm taking the Jeep out in a week so I need to get this done quick.

Should I use the proportioning valve that's already in there and just get some extra brake line to run to the MC, or should I use the one that is on the new booster already?

Here's what everything looks like so far, you can see the old proportioning valve in the bottom left of the picture..



I'm also not sure what I need to do exactly to get extra brake line and bend it so it will fit??
 
XJLI said:
both those prop valves are identical. so remove on or the other (whichever is easiest) and just bolt everything back up.
Click to expand...

Alright I wasn't sure if there were some differences on the internals I just wasn't aware of. Good to know.

The prop valves may be identical but the MC isn't. Either one I decide to use, I'm going to have to figure out how to lengthen those brake lines and wrap them around something or another.. Just not sure how to go about doing that?
 
its been a while, but i remember swapping to the WJ booster/MC on my 93XJ and i dont believe i had to make new brake lines? pretty sure they were in the same spot and i just bolted them up.
 
It looks like it might work if I just take the brake lines off the new prop valve and put them on the old one and hook it all up..

The problem is the ports are on the opposite side of where the old MC hooked in so I can't use the ones that are on there right now.
 
Thanks for the input everyone!

I bench bled the MC, got the brake lines all flared up right and hooked in, brake booster and everything is now hooked up and bolted on.

The only thing I need to do now is bleed all the brakes and get the rod from the brake booster to hook into the brake pedal but it's being stubborn as hell. I can get it hanging awkwardly off the side of where it hooks into the brake pedal but not far enough to get the clip on. Any suggestions?

Oh, and does anyone have a good lower back I could borrow?
 
Well, good news folks... Everything is all back together! Got the push rod on, brake lines all taken care of (only 1 of them is leaking, awesome!), and my brakes work better than they ever have! So good, in fact, that they don't release and are grabbing on all 4 tires even when I don't touch the brake! I'm so stoked!!








...Anyone interested in a 92 Cherokee on 35's, located in SLC? fml
 
After much trial and error, it's done. I ended up putting a second aluminum plate between the brake booster and firewall and that spaced the pedal out just enough to have it release all the way.

My brakes work fantastic, it's a night and day difference. For the first time ever since I've owned my Jeep I'm been able to lock those 35's up. I will wheel with a lot more confidence now for sure.

The only other issue I need to address is it seems one of my caliper pistons may be seized up.. There's always something else to do right?
 
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