MJ rear brakes

[rckrdyxj]

I am acquiring a 91 Mj long bed 6 cyl 5 speed for a daily driver/show truck project. I am going to be doing alot of different things to "update" this to a newer looking truck, such as the 98 front clip, interior etc etc. But one of the other things i am going to do is put a set of 2" coil spacers in with a set of take off 04 tj coils and some TNT 1.5" boomerang shackles to give it enough room to comfortably fit 30s for now and possibly 31 in the future if i feel like trimming (this is a street truck so i am not worried about flex)

 

I have owned 4 xjs and modded them plenty but ive never worked with an MJ before. I am also getting a 29 spline 8.25 with sprig under perches welded to it and 3:55's so it should have plenty of gear for 30s or 31s.

 

What my plans are as follows.

 

Swap in 8.25, new rear drums for now, Future KJ liberty 8.25 disc swap. Add the shackles and coil spacers.

 

My concerns are about that rear brake thingy attached to the axle, I should be able to use that on the 8.25 but how does lifting the truck effect that?

 

Also can i remove it completely and swap in a newer brake booster and proportioning valve?

 

 

When i did the rear disc swap on my xj i used a ZJ prop valve, so can i swap in my old XJ prop valve?

 

 

Basically whats the deal with the brakes on this thing? For now it will be stock front with 8.25 rear and drums, then one day rear discs.

[BLHTAZ]

If you are going to swap the booster and master to a newer style and use the front prop valve that comes with the new style, then you can easily do away with that rear valve and just plumb everything to match the new set-up. If you are going to keep the rear valve, then you will have to make adjustments to it when you lift the truck as the lift will cause the shaft running form the valve to the axle to be too short.

[rckrdyxj]

OK thats good to know then, What i am prolly going to do is swap out the brake booster or at least the prop valve from a 98 or newer xj and do away with the rear valve completely.

[mvusse]

If those boomerang shackles are designed to lift a Cherokee 1.5", as I believe they are, they will lift a Comanche only about 5/8". Not only is the stock MJ shackle 1.5" longer than a stock XJ shackle, but the amount of spring in front of and behind the axle are a 2:3 ratio, not 1:1 as on most vehicles. So a 5" longer shackle (which would be REALLY long) would be needed to lift the rear 2".

 

If the rear already sits higher than the front, it might look okay. If not I would have the rear springs re-arched, or buy a 3" lift pack from RE or MO.

[rckrdyxj]

Whats the best way to get a 2" lift out of an MJ? Rustys full length AAL? This is on a budget and i don't want to get involved wiht lift springs. Ive done aal lifts before but i didnt want the harsh ride in an empty MJ bed. I really don't have money for new springs nad i don't want any more than 2" really, i just wanna fit 30s. and make it look 4x4.

[mvusse]

You don't need a lift to fit 30s.

[BLHTAZ]

30's will go on without a lift, but they will be close and will likely rub a little now & then. The rear is no problem...just the front.

 

You could do something like this

[rckrdyxj]

I know that i don't need to lift to fit 30s but i would like it to look a little better and more 4wd vs the super low 2wd look that most 2wd trucks have. I know its the same height as a stock 4wd i just want a bit more but not as much as a full lift kit, just some coil spacers and sumtin in the rear. So i will prolly do a full length aal.