Transmission problem or other

Discussion in 'GM Powertrain' started by scott0303, Oct 30, 2009.

  1. scott0303

    scott0303 New Member

    Ive noticed a noise lately on my 99 GMC Sierra Z71. Im getting what I would call a clunk noise. Ive noticed it more when I am going around a curve and having to get out of the gas and then getting back into the gas. We noticed it while riding in the sharp twisted steep hills in the Smokies. It doesnt feel like anything is slamming into gear though. Tranny has 112K miles on it but was well maintened by the guy I bought it from. Even has a drain plug in the pan so I am assuming he had at least changed it once. Any ideas on what this could be. Definitely toward the middle to rear of the truck. Thanks
     
  2. Jimmiee

    Jimmiee Epic Member 5+ Years 1000 Posts

    Welcome to GMTC. The clunk could be a number of things. Have you crawled under the truck and looked? First check the U Joints for slop. Take a good look at the transmission mount and look for loose or missing bolts. Check the cross member bolts too. Usually clunks do not come from the transmission itself or transfer case. Check the rear spring bolts and the pinion flange while you're under there.
     
  3. scott0303

    scott0303 New Member

    Jimmie, I have gotten under there and looked around a little. How much slop would be noticeable with the ujoints? I dont know much about ujoints. Never had one go bad on any of my vehicles. Would it be something I could move enough by hand to know it was bad? Thanks
     
  4. Jimmiee

    Jimmiee Epic Member 5+ Years 1000 Posts

    U Joints can be tricky to diagnose. Usually a bad one will show rust or metal around the rubber cups. A bad U Joint may feel good until you jack up the rear end and get the vehicle weight off and the drive shaft free to turn. Also with the truck on the ground look at the U Joints while someone shifts between forward and reverse.
     

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