Rear Brake Issue has me puzzled

Hello, this is my first post and I look forward to further interaction with . I recently purchased a lifted/modified '01 XJ with 75k on the clock. Tires are 265/16 Firestone Destination MTs. Rear axle is the 8.25 without ABS. For the most part everything is good, but whenever it is slick outside (standing water, ice, snow, etc.) I have a problem with the rear drums wanting to lock up prematurely vs the front. I haven't had it happen when its dry or the tires have good/decent traction, but when its slick I either have to lighten up on my braking or else I get a pretty good jarring from the rear end. It doesn't really bother me too bad, yet I'm afraid that one day I'll be in the situation where I need to brake hard and then lose control of the rear end if it locks up early and starts to slide.

My question is, what could be causing this? I'm not positive, but it doesn't seem like the rear drums need pads, because like I said they stop fine when the traction is good, there is no squeaking or odd noises, and there is no sign of axle seals leaking. Is there a 'proportioning valve' of sorts in the braking system that could be bad, causing unequal distribution of braking power between the front and rear (ie. way too much in the rear)? Maybe air in the system? I don't have a 'Brake' warning illuminated on the dash or anything.

I'm curious what could be causing this. I'm a pretty good shadetree mechanic that could probably fix it myself, however I'd like to know where to start, or at least what to tell my mechanic to check if I dont' want to tackle on my own. Like I said, it isn't too bad most of the time but in tonight's 12"+ of snow it made for an interesting ride home.

Thanks for any help or insight you may have.

I recently had issues with one of our 96 XJ's. It would lock up the rears for no reason, wet or dry, but mostly when the brakes were cold. I decided to change the shoes from the Advance Auto Wearever brand that I had just put on it(that's when the problems began) to Wagner brand and the issue was solved. That was 2 months ago with no further problems.

I kept the shoes since they were new and installed them on my 90 XJ and they work fine on it. I really have no clue why this happened and why the shoes will work on the 90 but not on the 96.

it sounds like your front brakes suck, and the rear do not.

do your front brakes. use high quality pads. see what happens.

cal said:

it sounds like your front brakes suck, and the rear do not.

do your front brakes. use high quality pads. see what happens.

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I'm not quite sure thats the case. When I say 'prematurely' when talking about my rears when slick outside I mean this: if I get anywhere near 50% brake pedal travel with any intensity (not feathering it), both rears lock up suddenly which causes extreme jarring in the rear end (and some sliding around as well)

Front pads were replaced not too long ago, and rotors don't seem bad as I have no wheel shimmy, squeaking, etc.

If my fronts suck so bad that the rears are locking up when they do, then gawd I'd have the most sensitive brake pedal/system that I've ever experienced.

sovaxj said:

I'm not quite sure thats the case. When I say 'prematurely' when talking about my rears when slick outside I mean this: if I get anywhere near 50% brake pedal travel with any intensity (not feathering it), both rears lock up suddenly which causes extreme jarring in the rear end (and some sliding around as well)

Front pads were replaced not too long ago, and rotors don't seem bad as I have no wheel shimmy, squeaking, etc.

If my fronts suck so bad that the rears are locking up when they do, then gawd I'd have the most sensitive brake pedal/system that I've ever experienced.

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pull the drums off and post some pictures. something may be installed wrong.

If you have the coin & the willingness...
Go ZJ rear disc.
Drives great in the snow.

The rear brakes on my 98 would lock up like that after a water crossing. If I rode the brakes as I went through, it wouldn't happen. So I adjusted the drums and it would cure the problem for a little while.
But the self adjusters didn't work well and neither did the drums. Didn't figure that out until I converted to discs. Big difference when the rear brakes actually do something.

Could be crummy brake shoes that are grabbing, could be that the rear brakes are adjusted too tight, which could be caused by the self adjusters not working properly, could be the proportioning valve. Brake shoes are cheap, I'd consider inspecting the rear brakes to see what you might find, mess with the adjustment a little, then maybe have the drums turned to get rid of any potential bad spots, and start fresh with a good set of brake shoes.

Ronbo said:

The rear brakes on my 98 would lock up like that after a water crossing. If I rode the brakes as I went through, it wouldn't happen. So I adjusted the drums and it would cure the problem for a little while.
But the self adjusters didn't work well and neither did the drums. Didn't figure that out until I converted to discs. Big difference when the rear brakes actually do something.

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Even in South FL, my XJ did that when there was a lot of moisture in the air. When that happens or I suspect that would happen;... and it did happen after every downpour even if the road had dried before I got under way, I would simply drive with one foot on the breaks and one on the gas pedas for about 100 yards. That would cure all symtoms for the entire trip no matter how long. I would definately blame it on the quality of brake shoes not the state of repair/dis-repair of the rear breaks.

I've read that a common issue for these trucks was that in wet weather the rear drums would lock up on the first use, but be fine after that. I had the issue on my XJ for a while. Is this what you're describing? Is it only on the first use after sitting for a while?

If it's constant i would check out the rear drums overall, adjust the shoes, and possibly replace the hardware (springs especially). I would also make sure the fronts don't have anything on the pads (grease, etc.). The last thing i'd look at is the proportioning valve. If it's stuck you'll get too much rear bias.

OK...So, the backs should lock up before the fronts on a non-ABS vehicle as it might be nice to be able to steer the thing... Some ABS systems (my Wife's 96 Full Size Bronco for instance) only have ABS on the back brakes to stop the lock up. This allowed (under specific circumstances) the fronts to lock first. So ABS on all 4 was put into place.

Porch951 said:

I've read that a common issue for these trucks was that in wet weather the rear drums would lock up on the first use, but be fine after that. I had the issue on my XJ for a while. Is this what you're describing? Is it only on the first use after sitting for a while?

If it's constant i would check out the rear drums overall, adjust the shoes, and possibly replace the hardware (springs especially). I would also make sure the fronts don't have anything on the pads (grease, etc.). The last thing i'd look at is the proportioning valve. If it's stuck you'll get too much rear bias.

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You hit it right on the head. It happens only in wet weather be it rain in South Florida or snow in Des Moines it lock up on the first drive of the day and on the first break application or two all be it at the wrong time like trying to stop behind a stopped vehicle with traffic aproaching from the opposite direction. This happened for several years. I did nothing to fix it since it only happened on the first application or two. Funny,..I did not have this problem with the 1994 XJ I had before the 1996 (and a half) year model I now have.

I have seen this happen when there is moisture and alot of brake dust in the drum. I would thoroughly clean the rears and see how it behaves then.

jeeperjohn said:

I have seen this happen when there is moisture and alot of brake dust in the drum. I would thoroughly clean the rears and see how it behaves then.

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I guess the build up of break dust may well be (or at teast part of) the problem. When ever I clean inside the drums the problem would go away for a while. I now run the WJ disks in the rear so no more lock-up afer a rainy night.

Mine stopped doing it after i completely rebuilt my drums. In retrospect i wish i had gone disc. My understanding was that Jeep never really figured out what was causing the initial lockup.

One thing i've always done is grind down about 1/4" of the leading edge of the shoe at an angle. I used to get some strange noises from drums before i started doing that.

Check for and debris in the shoes, hand adjust the drums and what everyone else said.

How much is it lifted? Are the ebrake cables super tight and pulling on the brakes?

94xjstud said:

Check for and debris in the shoes, hand adjust the drums and what everyone else said.

How much is it lifted? Are the ebrake cables super tight and pulling on the brakes?

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Rubicon Express 4.5". I think my parking brake is adjusted correctly. No major tension in the handle, and it holds well when applied.

Like others mentioned, this usually only happens when the brakes are 'cold' and on slippery surfaces. After they warm up, I don't notice the problem as much. I'll take the drums off and do an inspection soon to see if I can figure it out. Probably crappy pads, out of adjustment or excessive brake dust in the drum.

techno1154 said:

I would definately blame it on the quality of brake shoes not the state of repair/dis-repair of the rear breaks.

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My issue occured with the OEM brakes, so I won't blame quality. This didn't happen when new, but after a few years and thousands of miles. Shoes were still in spec and worn evenly, so I didn't replace them.

Mine just started doing that the other day. I live in AZ and it was a dry day. I did go about 1/4 mi down a muddy trail when it started however. But this problem of touchy rear brakes continued sporadically for the rest of the day even after pressure washing what little mud there was on the Jeep off. I have 35k miles on the brakes and they are still in good condition. For me the brakes work just fine most of the time, but then suddenly with very light pressure on the pedal, the rears will lock up.... All I can figure is the brake proportioner valve.

For those of you who have done a rear disc swap, how smoothly did it go? Is it direct bolt up from a Grand Cherokee parts or is there any fab work? Been considering the swap, especially now.

I use all long brake shoes on mine instead of 2 long and 2 short shoes. It gives me noticably better braking.