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Weird driveline vibration on 99 K2500 Suburban

Discussion in 'GM Powertrain' started by Tachyon, Aug 15, 2011.

  1. Tachyon

    Tachyon Rockstar 100 Posts

    Hey,
    We're driving across Canada and the Suburban was running great until we picked up an odd vibration that I think is in the drive line.
    At about 100 Km/h the vibration starts and gets worse upt to about 110 then fade back off until it's relatively smooth again at about 120.
    The best way I can describe it is a combination of a wheel needing balancing and running over those idiot strips that mark the shoulder on some roads.
    The vibration is not in the steering wheel an seems to come from the chassis and under the floor.

    This truck got a new engine and transmission a few months ago along with a new front drive shaft (reman on the shaft actually) and new rear u-joints.
    This is a small block truck, originally a 5.7l but now a 6.2l (HT 383E upgrade crate motor) and the Trans is a new 4L80E. This is not an Autotrack vehicle. It has a manual 4x4 shifter on the floor.

    Any ideas on the cause of this?
    Anything I can try on the road? I have a basic tool kit (sockets, wrenches, screw drivers, multi-meter)

    Going to try and make it to a dealer nearer to home, but that's still a 10 hour drive.

    Any help would be appreciated.
    Last edited: Aug 15, 2011
  2. dpeter

    dpeter Rockstar 3 Years 500 Posts

    Hope things are still going OK that far from home. Drive shaft may have thrown a weight, look for signs of bare metal or different small rust spot where a weight may have been. I would also check to make sure the u-loints are still centered and seated properly in the yokes.
  3. Tachyon

    Tachyon Rockstar 100 Posts

    LWell, we made it back to the dealership where we get most of our work done. They are checking it now.
    Fingers crossed for something cheap and easy to fix.
  4. Wrench turner

    Wrench turner New Member

    Tachyon, What caused the vibration? Transfer case bearing?
  5. Tachyon

    Tachyon Rockstar 100 Posts

    Solution

    Sorry about that. I hate when people don't come back and finish a thread and now I've done it. Oops.

    At first we had the rear U-Joint replaced. It was in bad shape. But that was IMO caused by the vibration, not the cause of the vibration.
    The problem was that the top one or two bolts holding the transfer case to the transmission had come loose. The dealer that installed it felt like it was probably their fault so they fixed it for free.
    It's been fine since.
    It was tough to diagnose though because it felt like it was coming from under the floor behind the front seats. That's why the first shop went at the U-Joints first. My guess is that once the vibration started it setup a secondary vibration in the driveshaft and that's what we felt inside the vehicle.
  6. Wrench turner

    Wrench turner New Member

    Glad to hear it was something cheap/easy to fix.I appreciate the insight. I have a newly acquired 2000 GMC Sierra Classic K2500 in the shop for the same type of vibration. They have replaced three of the u-joints and the carrier bearing so far. I've heard the culprit to be the output bearing on the transfer case in another forum. I'm going to ask the mechanic to torque the transfer case to tranny bolts as a first step, thanks to your information. Maybe I can save a few hundred dollars. Thank you.

  7. Tachyon

    Tachyon Rockstar 100 Posts

    Good luck, I hope I could help. Also check all your mounts and mount fasteners. Then your driveline alignment and angles.

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