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wj booster/ mc swap


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in case someone isn't folowing my brake saga, here is what i did to fix it. i swapped out the booster/mc with one from a 99 wj. it was as easy of a bolt in as could be. the brake rod was the same length as was the hole for the pedal. i used some washers to space out the booster from the firewall a little and did a little bending of some sheet metal. used the brake lines that came with the master and re-flared the ends to match the xj prop valve. bled the brakes and the pedal feels amazing, much better then when the jeep was new. i have just a little air trapped still but with a re-bleed with a buddy and the brakes will be dialed.

i picked up the booster/mc from ebay from a guy parting out a 99 wj for $50 shipped to my house. it also came with the abs unit which i am going to try and resell.

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got the idea from here-

http://www.4x4wire.com/jeep/tech/brakes ... /index.htm

i didn't have to do any of the pedal rod mods like he did though.

i will give an update in a few days.

nathan

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Thanks for posting this I may just have to do it when I put in my D44 with a disk conversion on the rear as well. I think it is prob a better unit in all since everyone is so tough about saftey and such but as we all know NEWER isnt always better but in this case I think you did yourself a favor.keep up the good work jamminz.gif

 

Cole

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what other types of mc/boosters can be used? i though another member tried a ford fullsize van? does the WJ mc actually give more stopping power?

 

or something similar? i would like more stopping power than i have...

 

I'm going from 235s to 33's soon and my truck doesnt stop that great on the 235s so i know its gonna be a totalpig after the lift/tires

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i used some washers to space out the booster from the firewall a little and did a little bending of some sheet metal.

 

If you had to do the above, you should have used the 95-96 master/booster because it would not have been necessary. The 95-96 combo has a 1/4" aluminum spacer plate & gasket which snugs right up to your existing 91 firewall w. no leaks. No mods necessary for the pedal either, bolts right on using the existing clip.

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i used some washers to space out the booster from the firewall a little and did a little bending of some sheet metal.

 

If you had to do the above, you should have used the 95-96 master/booster because it would not have been necessary. The 95-96 combo has a 1/4" aluminum spacer plate & gasket which snugs right up to your existing 91 firewall w. no leaks. No mods necessary for the pedal either, bolts right on using the existing clip.

 

Would it bolt right up to an 88 MJ?

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No it will not. The pedal is different 1990 and below, so mods will be required. Either you have to get the 91 or above pedal assembly, or redrill the booster arm hole into your existing pedal, or get the pre -91 booster arm installed in your new booster. It's explained in detail in the link I posted previously in this thread.

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Oops, just noticed - Pete posted the link. I've only done it on my 91, which was pure bolt in. Easiest way is to pick up a 91+ pedal assembly. Also, the booster arm for auto and manual trannies bolt on opposite sides of the brake pedal, so get the correct pedal assembly for your application. No experience here on pre 91's, just what I've been told by guys who have done this mod.

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i used some washers to space out the booster from the firewall a little and did a little bending of some sheet metal.

 

If you had to do the above, you should have used the 95-96 master/booster because it would not have been necessary. The 95-96 combo has a 1/4" aluminum spacer plate & gasket which snugs right up to your existing 91 firewall w. no leaks. No mods necessary for the pedal either, bolts right on using the existing clip.

if you read the post right above your first one, that was my plan but i could not find one at the right price. for a newer booster/mc, i will bend a little sheet metal. :cheers:

nathan

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Oh crap - sorry I missed that Nathan. You've come up with another viable option. It's amazing what an updated booster and master cylinder does to improve the brakes. It's also amazing why Mopar/AMC waited all those years to give these vehicles decent brakes. It's not like the technology wasn't there. Don

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Oh crap - sorry I missed that Nathan. You've come up with another viable option. It's amazing what an updated booster and master cylinder does to improve the brakes. It's also amazing why Mopar/AMC waited all those years to give these vehicles decent brakes. It's not like the technology wasn't there. Don

agreed. my wife drove it for the first time since the booster swap and said it is like driving a whole new truck.

nathan

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i used some washers to space out the booster from the firewall a little and did a little bending of some sheet metal.

 

If you had to do the above, you should have used the 95-96 master/booster because it would not have been necessary. The 95-96 combo has a 1/4" aluminum spacer plate & gasket which snugs right up to your existing 91 firewall w. no leaks. No mods necessary for the pedal either, bolts right on using the existing clip.

 

dumb question... 95-96 XJ ?

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  • 4 months later...
Bringing back an old thread but can I just bolt up a 96 XJ master cylinder to my 89 booster or do I have to use a newer booster also? I got one off ebay for $20.

 

My understanding is you need to swap the whole unit, along with a pedal assembly out of a newer XJ. Been looking into this mod as well. Maybe someone can clairify it for us. :cheers:

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I don't know if this helps you much at all, but I'll pass along the info anyways. I swapped in the WJ booster at the same time that I swaped in my '99 XJ D30 and 8.25. After the fact, my MJ stops much quicker than my 98 XJ DD does. What I did to circumvent all of the hassles with the pedals and the booster rods was this: I simply cut off the rod end from my '88 MC and also cut off the rod end of the WJ MC. Then I just welded them back together, and shazam I had a master cylinder and booster that fit my needs. I did have to beat back the pinch seam in the engine bay, and a few misc other things, but that's my story. If you want some more info from me, let me know I can answer some questions for ya.

 

All that to say, I assume you'd run into the same story with the '96 booster. Why swap all of the pedal linkage when you can just cut and swap the rod ends. On the other hand, if you have no access to a welder (I remember what that was like) seriously- find somebody to do it for ya. It's gotta be easier than swapping the entire rod or pedal assembly.

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So you think I'll probably need the booster to go along with the master cylinder? There is a WJ combo on ebay right now for like $50 but if just the XJ master cylinder will help I'll try that first. And since I don't know much about brakes, will it really help or would the big improvement be seen in a better booster?

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The booster is the main thing that you want, as far as I know. The older (what was used in the MJ from the factory) is a single diaphragm booster. The WJ, as well the late model XJ's have a double diaphragm booster. I couldn't tell you all the specifics, but in short- it's better. I assume it multiplies the force put on the plunger in the MC at a higher ratio than the single booster. I don't know if I'd go through the trouble without getting some serious benefits, which the WJ setup does provide.

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