i have the gm 1 ton cylinders now, new shoes, new calipers, new pads...and ive been struggling to get everything adjusted and finally leave the brakes alone....i have bled everything and pedal travel is great...i have 4 WHEEL ABS

anyways i was driving last week after bleeding all the brakes...and after 2 hours of driving, my brake pedal started pulsign when i applied it and my rear brakes with suddering/hopping (locking unlocking very fast)...i still stopped...and pedal travel was still the same...its like my abs kicked in...it would have scared any passenger i would have had....anyway the ABS/brake light came on and stayed on.....got home....bled the brakes again...light went away...everythign was fine...2 hours later of driving....same thing....and the light went on again...and same anti lock type shudder

???

ive been reading about the RWAL? ive been reading about guys taking the ABS pump fuse out?...rear axle speed sensor??..and ive been readign about bad drums( but they're not cracked and seem good)

 

Could they be out of round?

 

yeah i guess.but this all started happening after i recently changed everything...including the booster, shoes, and upgraded to the gm 1 ton cylinders...i just can't get things to relax...what about adjusteing the parking brake? do i have to do that manually? or is that done automatically when i adjusted the rear shoes...

 

well i pulled the abs pump fuse from the driver's side box under the hood and no more shudder...so i guess that takes the drums out of the equation....since its the rears doing it im thinking RWAL...and also the speed sensor on the rear axle?

 

I'd think that you might have too much braking power to the rear at the moment so that the ABS is kicking in for good reason.
You can try to shorten the rod of the proportioning valve a bit- a redneck version to get an adjustment is to pull the rod and zip tie it in the desired position on the axle and after some tries to determine the correct position to measure the distance from the balljoint on the axle to the balljoint on the proportioning valve and fabbing a new rod with the right dimensions.

HTH

AlpineRAM

 

good lord!..thanx alpine ...first where is the proportioning valve? what is it responsible for?...ps i think u may be right about the braking power...since the big cylinders, this truck can stop!

 

can someone tell me where this proportioning valve is located? somewhere on the rear axle?...for now i D/C the abs fuse and no more shudder but i would like to adjust this valve so that the system doesnt keep overreacting to the power of the rear brakes

 

'95s don't have one.

 

I think you have the rear shoes adjusted too tight. I had this problem also. try driving awhile and stop gently. Get out and feel the drums. If they are really hot (too hot to keep your fingers on) then you may have to back off the starr wheel 1/2 turn on each side.

 

yeah well i originally tigthened them to the point of rubbing and then backed off about a full turn...i guess i could back them off more i just dont want my pedal to get too soft...maybe I'll try and bleed the RWAL and all the wheels since ive been changing calipers and cylinders

 

Umm....silly question.

Did you put everything back the way you found it?

It's worth a re-check.

 

I have had the exact same problem since I installed new shoes and wheel cylinders. Frankly, it is dangerous, and with winter coming and ice, I need to get it fixed. I had the drums turned to no avail. One thought I have is did I put the shoes back in correctly? Does the longer larger shoe go in the front towards the cab, or in the back towards the bumper? I will pull my rear ABS fuse and see if that works in the meantime. I am also wondering if I knocked something lose when I put it back together. Anyway, it is pretty **** scary and I only thought it was me!!

Thanks for any advice you can provide on shoe location.

Ty

 

primary shoe/big shoe goes on the back...yeah there have been a few guys who had trouble getting things to tune right after the bigger wheel cylinders and new shoes...