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Rear wheel lockup

Discussion in 'Chevy Trucks' started by MarkEagleUSA, Dec 27, 2010.

  1. MarkEagleUSA

    MarkEagleUSA Senior Member
    Messages: 335

    So our first storm of the season dumped over a foot of snow and I finally got to use my new (to me) 97 2500. Everything was great until I went to go down my driveway (about a 30 percent grade). The slightest tap of the brake pedal caused the rear wheels to lock putting me sideways across the driveway.

    I checked for problems with the front brake lines but they were fine. I also checked the master cylinder and it was full. The lockup continued for the entire time it took to clear my driveway. Then when I attempted to drive to work and the problem was gone... no more lockup.

    Does anyone have any idea of what could be wrong and what I should be checking? Could it be a problem with the RWAL controller under the hood? Maybe a wheel or speed sensor packed with snow?

  2. sweetk30

    sweetk30 PlowSite.com Addict
    Messages: 1,588

    the good old gm 3/4 ton -1ton rear brake damp / grabby / lockin up brakes when cold first run.

    when thay sit and go cold over night or all day then you use them thay can lock up the first hit or 2 . then drive fine all day.

    there is a few fix's for this out there if you want to. search gm truck rear brake lockup. should come up.

    and yep you found out it can be a bit tricky till you get use to it. my self and a friend drove ours for few years like this and just ignore it.
  3. Detroitdan

    Detroitdan PlowSite.com Addict
    Messages: 1,937

    Mine does it because of a slight seal leak that lets gear oil get on the shoes. I've replaced shoes and seals enough times, cant seem to fix it so now I ignore it, and add about 3 ounces of gear oil a year. All I have to do is drag the brakes lightly for a couple hundred feet when they're cold, and a little heat in them fixes the problem. Even if your problem isnt oil leaking, dragging them might fix them. But I would recommend pulling the wheel and drum, just to make sure if you do have a seal leak it isnt a bad one.
  4. MarkEagleUSA

    MarkEagleUSA Senior Member
    Messages: 335

    Good? :eek:

    Makes sense I guess... except I don't understand why they lock up with RWAL. Oh well, I'll read up on it a little more and see if I can do something to help the problem. Thanks.
  5. mcwlandscaping

    mcwlandscaping 2000 Club Member
    Messages: 2,557

    If the rear brakes are not adjusted right it will do it...happened on my 97 all of a sudden and that was the problem
  6. Detroitdan

    Detroitdan PlowSite.com Addict
    Messages: 1,937

    you have rear wheel abs?
  7. MarkEagleUSA

    MarkEagleUSA Senior Member
    Messages: 335

    Yes... the truck has RWAL.
  8. marylandbigb

    marylandbigb Member
    Messages: 87

    if i remember correctly in 97 and some other years the abs was deactivated when vehicle was in 4wd. another thing too check see if you have riveted rear shoes or bonded rear shoes bonded always lock up when cold on a gm vehicle if bonded go too a rivetd shoe make sure they r installed correctly too shoes on backwards can cause this too and make sure the drums r smooth if not resurface or replace them good luck
  9. MarkEagleUSA

    MarkEagleUSA Senior Member
    Messages: 335

    This morning I had the lockup again and the truck was in 4WD. Put it into 2WD and the lockup went away.

    What really puzzles me is why are they locking up with very little pressure applied to the brake pedal? I could understand if I was on the brakes, but in my case just the slightest of pressure on the pedal is causing them to lock.

    With only minimal pedal pressure in 4WD causing it and no lockups in 2WD, I'm thinking it's a problem with the RWAL controller even though the brake indicator isn't coming on nor is the truck throwing any trouble codes.

    It will be tomorrow night or Thursday afternoon before I'll have any time to pull the wheels and take a look to see if there's anything going on inside the drums.
  10. marylandbigb

    marylandbigb Member
    Messages: 87

    thats why i believe the abs is deactivated in 4wd which will allow lock up. in 2wd abs reactivates not allowing the wheels too lock up . remove the drums when you can and take a look. u may have an axle seal leak wheel cylinder leak or even an excess of dust that gets damp and causes it. and like i said if they r bonded shoes thats a good start for ur concern good luck
  11. MarkEagleUSA

    MarkEagleUSA Senior Member
    Messages: 335

    Another morning and more lockups in 4WD. As soon as it locked up I put it in 2WD and the lockup went away. Tried 3 or 4 times - nothing. Put it back into 4WD and boom!... lockup.

    This has to indicate a problem with the controller doesn't it? What else could explain the difference between 2WD and 4WD (assuming 4WD deactivates the RWAL)? Puzzling to say the least. :confused:

    Hopefully when I get home this afternoon I can pop the wheels off and have a look.
  12. MarkEagleUSA

    MarkEagleUSA Senior Member
    Messages: 335

    Finally had some time to check this brake problem out.

    First thing I did was pull the ABS fuse but that did nothing to eliminate the problem so I guess I can rule out the RWAL controller.

    I pulled the rear wheels and found no leaks from the wheel cylinders or seals. There was a bit of dust on both sides so I washed everything down with brake cleaner.

    The brake adjustment seems fine on both sides and I'm running riveted shoes that don't appear to be worn (at least not needing replacement yet). The drums look fine also.

    Yet the problem continues. Lockups occur both forward and reverse at low speed. After a few minutes it appears to clear up. At this point I'm going to live with it until I can do a complete rear brake job. I'll replace everything and start fresh. Any recommendations on what shoes are better: semi-metallic or ceramic?
  13. Sp3cialized

    Sp3cialized Member
    from CT
    Messages: 58

    See, I pulled my ABS fuse and now my problem went away.. but similar to yours in that I was trying to 'hunt' it for a while and nothing was popping right out at me!

    Im not in the mood to replace the ABS controller on this truck...
  14. jchart06

    jchart06 Junior Member
    Messages: 25

    ABS in those years doesnt function in the rear under 29mph and 15mph on the front. is one wheel or both?