hey all, i have been having an issue. my 93 d150 has a bounce in the back when braking at any speed. over the past couple months changed drums,shoes,wheel cyls.,hardware,rear springs,shocks,u-bolts. it also has new wheels,tires. it also did this before i replaced all these parts.
some info leads me to believe that it is the ABS module?? i have no ABS light on. could this be the main problem?? thank you

 

My RWAL brake light never came on, even when the rear control valve totally locked up and would allow no fluid to get to the back brakes. This system was a poor first shot at ABS in my opinion. How this could cause a bounce though I cannot fathom. A pulsation is possible from a failed RWAL system. I bypassed the rear control valve in my truck.

 

the computer that is suppose to control the abs should be behind the glove box. i unplugged the one on my 91. never knew if it worked or not. never saw a light.

 

i know its old post. i just been living with the problem.
i just unplugged the abs control,and there was no change still bounce.
no abs light on either. i know the abs light works,its on when i first flip the key on,then goes out when started.
does any of this mean the abs control is good?? what else could it be??
i have just been putting these annoying problems on hold for a while.
thank you

 

Just unplugging the RWAL module does not take the entire ABS system out of the brake system. It merely eliminates automatic electronic control. The rear hydraulic control valve is still in the system and can even if rarely mess with braking. Mine failed and blocked all fluid from getting to the rear slave cylinders. IE: No rear brakes at all on my truck.

 

I don't mean to be this guy who throws a random monkey wrench in there at everybody. Obviously, you know what you are doing, probably more so than myself. But how are your shocks? You would think that if the valve were stuck, it would be stuck in one position.

 

i think he might have new shocks already. i think he replaced those while trying to take the shake out of his truck. with how many new parts are his truck it has to be close to showroom condition.

 

"You would think that if the valve were stuck, it would be stuck in one position." I agree with you wontacceptthis, and that is what I said in my first post of this thread. At this point there isn't much left that he hasn't done or replaced with new parts.

Since his question now is "could the ABS be causing this" I think bypassing the ABS hydraulic control valve totally is the only way to completely rule out the ABS system as a possibility.

Did you haul any very heavy loads or hit any big holes before this started? Is a bent axle a possibility? Could what you are feeling be described as a wobble instead of a bounce?

 

well i know its not a bent axle,i checked that out with dial indicater.
it sure feels like bounce,bed and truck shake up and down, real bad going 30-45 with light pressue on the brake pedal. thank you

 

could the tires be the problem-a broken belt