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RR brake "grabby" on '87 3/4T 'Burb, tried everything...

Discussion in 'Chevy Trucks' started by uglytruk, Feb 11, 2006.

  1. uglytruk

    uglytruk Member
    Messages: 74


    If it's not one thing, it's another. I just did a ton of suspension and brake work on my newly aquired 87 3/4 ton 6.2 Burb. When I test drove it last week, the right rear brake was "grabby". So even though pulling the drum showed no oil or weird stuff, I changed the shoes anyways. I ground off the "lip" to make it easier to re-install the drums, (13"), ground down the wear spots on the backing plates and made sure everything was up to snuff. Anti-sieze in all the right places, cracked open the bleeders to let the fresh fluid run through, and new calipers in front.
    The RR ebrake cable was toast, so I installed a slightly shorter one, and adjusted the whole lot carefully. And that's where the trouble began. The return spring on the front (cab) cable is weak, so the ebrake pedal won't return to put out the light. No problem, I 'll put a wire clamp on to "shorten" the spring. A test drive wasn't promising. The RR started to grab after a few easy miles, I backed off the ebrake, thinking it was a little tight. No dice. This morning, (5f), I pulled the drum off, expecting to have to back off the shoes or maybe a sticky cylinder, Nope, drum came right off! Weird! I double checked free travel of cylinder pistons, smooth travel of shoes, cracked bleeder, yadda, yadda. Thinking I was just having bad luck, I traveled 40 miles to Vermont. Upon arrival, it's doing it again. Didn't touch ebrake, cold outside, no mountain decents, just grabby, slightly applied feel. I cracked the RR bleeder, a bit of oil trickled out, and off came the drum again in a bookstore lot. Again I expected the drum to be held by the shoes, but no! What's going on? I put a small ViceGrip on the rear rubber hose, cracked the bleeders, and drove 30 or so Interstate and 2ndary miles to the ferry to cross the lake. and it did it again! Thinking some oil leaked past the ViceGrips, I left the bleeders open, but the RR was still doing its weird dance.

    OK, I give up. Maybe I should try a different drum. I have a '79 2wd 3/4t. 16.5 wheels, but same drum? If it was the master cyl, it would affect BOTH back brakes, not just the RR, right? Backing up makes it worse, and I got the leading/trailing shoes right. Remember, the previous shoes exibited similar behaviour.

    I'm formerly an ASE licenced mechanic, so this problem really stumps me...
  2. ght1098

    ght1098 Member
    Messages: 86

    Try disconnecting the parking brake cable. I had an 88 dodge that did the same thing, was the parking brake cable. Good luck.
  3. calponte

    calponte Junior Member
    from MI
    Messages: 7

    Master would affect both.. but would affect the one closest to it more. And being the RR.. it doesn't make sense. Get rid of that e brake and get a new drum. If that isn't it..then you've installed the guts improperly in the shoe, thus exaggerating the automatic adjuster which is actuated by backing up.
  4. uglytruk

    uglytruk Member
    Messages: 74

    Pretty good answer, but I think I have a handle on it.
    The wheel cylinders are original, 19 years old, so I changed the RR one to-day, and opened it up afterwards. It was pretty slimy inside, but I'm not convinced that it was sticking. I also couldn't get the correct RR ebrake cable, so I had installed a 4" shorter one and welded an extra 4" onto the threads. But the right brake would be adjusted just right, 1/32" play on the strut with the shoes just backed off the drums. But, the LR would be loose like hell, (the ebrake), to the point where the pedal would only grab the drums right at the floor. So after scratching my a**, I ordered the correct cable, will install to-morrow, along with LR cylinder. :rolleyes:
    Drove it a bit to-night, and pedal is decent, and no grabbing! I also repaired the ebrake pedal, as the tiny spring that pushes the ratchet down to lock the applied pedal was weak. Can't wait 'till partz are installed...
    Last edited: Feb 13, 2006
  5. Jpocket

    Jpocket Senior Member
    Messages: 302

    Alll of the OLD Chevys do that from time to time, I had a 76' dually that did it, and my 85' 2500 does it now, the brake break seems to lock up while the rest of them are normal
  6. uglytruk

    uglytruk Member
    Messages: 74

    I also thought (but didn't tell anyone), that I let air get in while I was letting the lines drip out the old fluid. Maybe the air was heating up and expanding, even though it was barely above zero, 13" monster drums, and I was driving like the old man I'm becoming. But it was probably the cylinder, even though the ebrake was tight. Just drove it a mile, seems fine... :angel:
  7. welded wrenches

    welded wrenches Senior Member
    Messages: 177

    GRABBY brakesss

    Hi.Been there.Mne was a a leaking axle grease seal.kept grabbiny ang locking up for the firstb10-15 mile. Also te the auto-brake adjuster threded do-hicky.Fits only left side or only right side only.They are not same. If on the wrong side they will keep loosing them selves.each time you back up and slam on the binders.