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ABS pulsing

Discussion in 'Chevy Silverado Forum (GMC Sierra)' started by nbturbo, Apr 3, 2012.

  1. nbturbo

    nbturbo New Member

    So one day in the winter when I took my 03 2500 silverado out the abs light came on, which has happened in the past when there was snow blown up around the wheels, a bit down the road light went off. Last week I drove it (it only gets used once every 2 or 3 weeks) and when I applied the brakes, I felt the abs pulsing towards the end of the pedal travel, like it would do if I was stomping on the brakes or they were sliding on ice. Today took it out again and the same thing, when I stopped at a light, the abs light and red exclamation light came on with a buzzer, but then they both went out when I started off again, brake pedal still pulsing. Brakes still working okay, any ideas on what can cause this?
    tks
  2. dipstick

    dipstick New Member

    Could be a sensor could be quite a few things . Need to scan for codes will get you started in right direction.
    Less money and time guessing at it.
  3. meandmyharley61

    meandmyharley61 New Member

    sounds like a bad front wheel bearing.
  4. elkhornsun

    elkhornsun New Member

    Most likely you have one or more bad ABS sensors. Not at all unusual for one to fail. Easily tested by the dealer to find the faulty one(s).
  5. shibby2oo8

    shibby2oo8 New Member

    Most likely a hub sensor, if you can get a graphing scanner graph all 3 speed and watch one drop out when it acts up. Also just getting a code and replacing the one it describes works 85-90% of the time. The nice thing about the trucks is the harness to the bearing is long and rules out bad jumper harness opposed to the cars. Scan it and give us a code.
  6. Pikey

    Pikey Moderator Staff Member 1000 Posts

    If you can't get a hold of a scanner, I would try jacking up the front end, grab the tires and give it a wiggle. If the bearing is really bad you will know it by how much that side moves. Every time I have had one go out I can move it significantly or you can hear it "crunching" or "squealing" when you rotate the tire. Just don't confuse brake pad on rotor noise with squeaking from the bearing.
  7. nbturbo

    nbturbo New Member

    Thanks everyone, got it scanned for codes, it showed right front wheel bearing abs sensor, then the mechanic did the speed test and confirmed it was the right one. Now, is this a complicated repair, is there a diy on here for it? I have an above average mechanical ability, and lots of tools.
  8. Pikey

    Pikey Moderator Staff Member 1000 Posts

    It is not that hard to do. The only special tool you need is a large socket big enough to remove the nut from the front cv shaft (assuming that it is 4 wheel drive. (I put mine in 4wd to hold the shaft so I could break the nut loose.) You can rent that from autozone for free. You may also need a pickle fork if you need to separate a ball joint. You can rent those for free also. Most the time you don't need to separate the ball joint. You will need to remove the Brake caliper and bracket. (The Bracket Bolts are hard to break loose sometimes) Other than that there are 4 bolts holding the hub assembly in. Access those from the rear of the knuckle. On 4x4 models there is not much room to get a wrench onto the hub bolt heads, especially when they are backed out a few turns. So, as you unscrew them, push in on the cv shaft and pull the hub out of the knuckle to give you room. It is pretty straight forward. Sometimes they can be a pain to get out. One of Mine took a lot of persuasion with a 5lb hammer. The other on came out rather easily. By sure to clean up the hole before you put the new one in. A lot of people recommend putting a new nut on the CV shaft also.

    ---------- Post added at 01:13 PM ---------- Previous post was at 12:44 PM ----------

    Here are some torque specs you might want, they are for an 02 but I assume that they are the same:
    Hub-to steering knuckle bolts: 133ft-lbs
    Caliper mounting(guide pin) bolts: 80 ft-lbs
    Caliper mounting bracket bolts (for 2500 model): 221ft-lbs
    Drive axle (hub nut): 155ft-lbs (I would double check this one, it seems kinda low, autozone might be able to tell you what it is)
    Lug nuts: 140 ft-lbs

    Hope these help
    Last edited: Apr 27, 2012
  9. nbturbo

    nbturbo New Member

    thanks Pikey, seems easy, and mine is a 2wd, so probably easier. What isn't easy is the price of the darned thing :)
    d
  10. nbturbo

    nbturbo New Member

    A mechanic friend of mine told me last night that it isn't advertised by the dealer that the abs sensor is available as a replacement part. The old one is usually ruined during removal, but it can be replaced. I have no side to side or up and down movement, no 'crunchy' sounds when the wheel is spun, so the bearing seems solid. He says he replaced many of them, including his own truck. The sensor is only $75, versus $200 for the whole bearing, any comments on this?

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