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Thread: Transmission shifts up and down when cold

  1. #1
    Join Date
    Nov 2007
    Location
    Central Up State New York
    Posts
    10

    Default Transmission shifts up and down when cold

    1995 Yukon 6.5 turbo diesel 4l80e when the truck is cold it shifts up and down, drive, overdrive and back until the truck comes up to temp then it's fine. Any thoughts on this?

  2. #2
    Join Date
    Feb 2007
    Location
    Baja California Sur Mexico
    Posts
    2,807

    Default

    You should have a code, retrieve it with a paper clip. May say that the temperature sensor in the thermostat housing is bad.
    Grant H.
    1995 6.5 turbo GMC K2500 extra cab 4x4 pickup, PMD under bumper, mechanical wastegate, 228,000 miles, rebuilt engine, 4.10 diff, 16 mpg
    1994 6.5 turbo GMC K2500 4x4 suburban "F" VIN #9 resistor, PMD in the bumper, mechanical waste gate, 226,000 miles, Positrac 3.73 diff, 17 mpg highway.
    1982 4x4 shortbed 6.2 Chev 260,000 miles untouched motor 17 MPG 4.27 diff. Best thing I ever owned, 21 years.

  3. #3
    Join Date
    Nov 2007
    Location
    Central Up State New York
    Posts
    10

    Default

    No codes
    .

  4. #4
    Join Date
    Dec 2006
    Location
    Chilliwack BC Canada
    Posts
    676

    Default

    replace the sensor on the thremostat housing thats what I did ...G
    2001 Chev ex cab short box
    D-Max / Allison 4 inch exhaust, reflashed ECM & Air induction

  5. #5
    Join Date
    Feb 2007
    Location
    Baja California Sur Mexico
    Posts
    2,807

    Default

    I agree, Garth, Just checked, and there is no code set when that mal functions.
    Grant H.
    1995 6.5 turbo GMC K2500 extra cab 4x4 pickup, PMD under bumper, mechanical wastegate, 228,000 miles, rebuilt engine, 4.10 diff, 16 mpg
    1994 6.5 turbo GMC K2500 4x4 suburban "F" VIN #9 resistor, PMD in the bumper, mechanical waste gate, 226,000 miles, Positrac 3.73 diff, 17 mpg highway.
    1982 4x4 shortbed 6.2 Chev 260,000 miles untouched motor 17 MPG 4.27 diff. Best thing I ever owned, 21 years.

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