99 WJ Booster/MC swap in an 89 XJ

Just wanted to save some people some trouble and time. I don't feel the need to post yet another write-up, but some bits of info that hopefully will pop up in a search:

1.) I drilled out the pushrod, but it seems there is just a metal sleeve in there that got stuck on the stepper bit. You could probably pop it out with something, and the nylon bushing from the XJ fit perfectly. No filing of the outside edge needed either. I "mic'ed it" with precision calipers - the difference was negligible.

2.) I did not need the spacer, although I spent a good amount of time fabbing up one. The brakelight switch works better/sooner than with the spacer. Don't know about cruise control, because that stopped working before I did this mod. Also, the pedal travel is slighly better than stock, and way better than with the spacer. YMMV.

3.) If you get a chance to do this mod - DO IT! (should be #1)

4.) Plan on replacing your proportioning valve and flaring some lines. Get a valve with all 3/8" fittings. Get a 25' roll of 3/16" tubing - trust me on this - pre-fab lines suck if you need to cut and make a flare!

5.) Don't cheap out on your brakes. (should also be #1)

6.) Buy another turkey baster for Thanksgiving. I have 2 now for brake fluid, since I thought I threw the other out.

7.) Leave the brake pedal unbolted until you bolt the booster to the firewall. You need room to move!

8.) I needed to make 3/4" sleeves for the bolts, since the WJ firewall rubbed the threads. The bolts are too long to be wrenching in that tight of a space, anyway!.



To be continued?

so it essentially bolted in minus getting the spacing right and flaring some lines? no need to modify the booster rod at all? and did you have ABS before this swap?

1990JEEPXJ said:

so it essentially bolted in minus getting the spacing right and flaring some lines? no need to modify the booster rod at all? and did you have ABS before this swap?

Click to expand...

When I did the mod I had to drill out the booster rod to fit the stock pedal bushing. I then filed the end flat like the stock rod.

Spacing the booster from the firewall was easy, just bought some washers. Flaring the lines to fit a ZJ prop valve was a pain, but it all worked out in the end.

The WJ I pulled the booster out of had ABS, my XJ doesn't. No real modification to the rod at all. The brake switch rests right on the pushrod at an angle and the brake lights work fine. I'll get pics up soon.

Brakelight switch:



Spacers go here:



Prop Valve:



I ended up putting some foam in between the booster and firewall to block any heat or stinky air in the cabin. The lines on the prop valve were reversed, since the rear chamber is in front of the MC, and the rear inlet is to the back of the prop valve. This worked perfectly, because the lines for the stock prop valve were the right length and wouldn't have worked the other way. I forgot to include a finished pic. The wheels won't exactly lock up on 31's, but I have to bleed again and the Ford 8.8 with discs isn't installed yet.

Didn't want to jinx it, but...

Do yourself a favor and only use single flares - they work just fine, and I learned that you only need a double flare when joining two LINES in a compression fitting. Essentially, that is what the mating port does, but don't rely on that "nipple" to be strong enough to crush the double flared line to fit. This is what happened to both of the OEM valves I had (thanks GrimmJeeper!), probably right at the factory.

New brake system already saved my butt!!!