2nd Gen Non-Engine/Transmission Rear brakes release under hard braking

[AggieJustin]

I've been having some trouble with the rear brakes on my truck lately. Under hard braking, it feels like the rear brakes are releasing leaving all the stopping up to the fronts. I can feel the rear brakes grab for a second or so when I first hit the brakes, but then it feels like the rear brakes just give up. And trying to stop with just the front brakes feels like trying to stop by putting my foot out of the door. If I release the pedal and re-engage the brakes, I can feel them grabbing again. Nothing like having to pump the brakes just to get some decent stopping power.



I was thinking of a couple of things that could be happening.



A. Whenever I brake hard and weight is shifted to the front, the proportioning valve for the rear brakes removes braking power from the rear wheels since it is detecting less weight.



B. The ABS computer is limiting the braking force of the rear wheels. I don't know why this would happen though since the wheels don't seem to be in any danger of locking up.



Does anyone else have any suggestions of what might be happening, or has anyone experienced this same behavior?? Whenever the brakes initially grab, they have good stopping force. If I could keep that kind of force the whole time I was braking I'd be happy.



Justin



P. S. The truck has 4 wheel ABS.

 

[baby.driver]

It's the abs sys.

Pumping the brakes will only confuse the computer.



Jay

 

[RThompson]

I posted on the same condition a while back. You may want to look this thread over. https://www.turbodieselregister.com/forums/showthread.php?s=&threadid=42142

 

[AggieJustin]

Thanks for the link RT.



baby. driver, it's not that I'm pumping the brakes quickly like you would to keep a pre-ABS system from locking. I just have to hit and release the brakes occasionally to reestablish more braking power. Once I drop to a lower speed, I don't feel the rears releasing anymore.



Do the 2001s with rear drums have a load sensing valve?? If so, where is it located at? If I have one I'll have to check it out to make sure nothing has happened to it.



I just don't like the feel of my brakes saying "No!!" when I say "Whoa!!"

 

[AggieJustin]

TTT

Wanted to see if anyone could tell me whether or not the 2001s with rear drums have a load sensing valve for the rear brakes? It's been raining here so I haven't had a chance to get underneath and take a look.



Since it seems they've been acting up more lately, I wanted to make sure nothing had happened to it (if there is one there).



Thanks,



Justin

 

[Gizmo 007]

Welcome to the club... Mine's done that exact thing since new. I've tried disabling, replumbing, different brakes, all to no avail. My truck has 4 wheel disc brakes, btw.



So... I built a custom front and rear bumper (3/16 plate with 1/4 wall square tubing) and threw a 30 gallon fuel tank in the bed. Seems to have solved the problem .



The back end of these trucks are too light, so DC tried to compensate by moving more braking force to the front wheels. Bad move DC !

 

[RThompson]

I pull fifth wheel with about 1600 lb pin weight and have 50 gal. auxillary fuel tank. Given some thought to trying different rear pads that might have higher friction coefficent. Anyone out there with some ideas for tweaking the ABS to help increase rear line pressure or what might be good choice for rear pads?