HARD shift after driving for 30 minutes

Discussion in 'GM Powertrain' started by RodneyB, Mar 25, 2011.

  1. RodneyB

    RodneyB New Member


    I have a 99 GMC Suburban LS 4x4, auto trans. I just bought this truck and previuos owner had it sitting for 5 months. I have put 500 miles on the truck.

    It shifts smooth as silk when running 20 minutes or less. If I run it longer, I get very HARD shift on 1st and a medium HARD shift on 2nd. Truck has 173k miles.

    Trans fluid looks good and does not have a burned smell.

    What steps should I take to resolve. Do the Trans coolers go bad and need to be replaced? Do I need to get a trans flush ? Do I ndeed a repair?

    Any help would be apprecaited.

  2. bigredtractor95

    bigredtractor95 New Member

    your valves in the valve body are getting hot and sticking

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