Rear brakes Locking up

[pennell]

I have been going to through hell to try and fix this problem. $1000 later, and my passender side rear brake STILL locks up when I touch the pedal. Happens maybe 50% of the time. My mechanic tells me its the POS abs module for the rear end, and I am noticing on here that most get rid of it.... Anyone else have the same problem as me, and did the ABS delete fix it? I am also doing a hydroboost conversion so I am guessing this would be a good time to get rid of the ABS module as well? Any input would be greatly appreciated.

Thanks

[Black93]

Just unplug the abs mod. and see if that fixes it. I unplugged mine about a year ago, because the abs light wouldn't go off.

[PJ 3]

My rear brakes on my truck locked up steady since it was new. I did a count on my warranty bills and it was into the garage 17 times
I unplugged the abs computer behind the glove box and by-passed the brake module on the rear frame and no more problems. One of the best mods done to my truck.
The parts are in the local land fill where they belong.......another mopar mystery

[pennell]

Sounds good. So I just unplug the ABS and if it doesn't lock up anymore, then I will just bypass the whole thing and toss it in the trash?

[pennell]

My rear brakes on my truck locked up steady since it was new. I did a count on my warranty bills and it was into the garage 17 times
I unplugged the abs computer behind the glove box and by-passed the brake module on the rear frame and no more problems. One of the best mods done to my truck.
The parts are in the local land fill where they belong.......another mopar mystery

I have spent $1000 and countless visits to the shop since November. Wish I had of posted this earlier!

[pennell]

Alright, so I got the ABS bypassed but now it seems like there is to much bias to the rear. If I have to hit the brakes quickly the rear wheels lock up and chirp... Help?

[CumminsPower59]

The rear brakes on my 92 do the same right after I get going with it, but then they are fine the rest of the day. Do yours lock up every time or just once in a while?

[Mark Nixon]

There are several different sizes of rear wheel cylinders out there.
Too SMALL of ones on the rear will lock them, too big of ones will have little or no assist to the rear brakes and locking up the fronts becomes a problem.

If you're locking up one side it's either contaminated with oil or brake fluid, or has an under-sized wheel cylinder.
I have also seen incorrectly installed brake shoes do some silly things.
There's a long and short pad on drum brakes.

Mark.

[bmoeller]

If you still have old brake shoes, I've seen cracked linings come apart and cause issues. Rust cracks the lining and tries to push the lining off of the backing plate. Damp wheel seal or leaking wheel cylinder will do it.

[PToombs]

If they're not adjusted close to the drum they will grab too. I don't know for sure, but I think it's because there's so much slack, everything has to kinda wind up before it grabs.
Or else they are moving fast by the time they hit the drum.

[PJ 3]

If they're not adjusted close to the drum they will grab too.

That would be my next move, adjusting the star wheel so the shoes slightly rub on the drum. I didn't have any problem after the mod, although I replaced everything with new parts and did the adjustment and that solved my brake issues for good !

[jdslucky]

even if it has new drums machine them.

we fought a drum brake system here at the shop for months and were about to replace the prop valve thinking a bias problem.
everything in the rear system was brand new.

drum brakes have to be clean of dust
adjusted properly like mentioned with a little drag
and make sure the drag is equal side to side
MACHINE THE DRUMS

[dpuckett]

So, Mark, you're saying I should have stuck with the smaller wheel cylinders to improve rear braking? Please elaborate. On a side note, the only two pickups I've had consistent brake issues have been W250s. Mine are going the other way- I ended up in the middle of an intersection yesterday because my brakes were not doing their thing.

[Mark Nixon]

Smaller wheel cylinder=less volume, quicker action.
Bigger wheel cylinder=more volume, slower action.

A smaller wheel cylinder will also stiffen the pedal, where the larger one can leave a "mushy" feeling.

Mark.

[ellis93]

I did the larger wheel cylinders,and I've no mushy pedal. Also if the pedal is stood on the rears wil slide before the fronts. Now I don't know what's different about what I've done,but I just do
n't have the side effects.

On another note,isn't there something about hydraulics that if 10lbs applied to a 2" cylinder would :: equate to 20lbs of force from the cylinder. It was something like that,I can't remember