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Thread: 4L70E 1st Gear shifting issue

  1. #1
    Tuner in Training
    Join Date
    Dec 2011
    Location
    Sanford, NC
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    25

    4L70E 1st Gear shifting issue

    Hello,

    I'm helping a buddy out with his 2007 Avalanche, 5.3L. Problem just started out of the blue. The truck will not shift out of 1st gear without lifting off the gas. Doesn't matter if you are WOT or just normal driving. The other gear changes are fine. There isn't a CEL. I have attached a log file and the current tune file. Any help would be appreciated.


    Current Tune file 12DEC2019.hpt
    19-12-12 18-39-49.hpl
    Last edited by Batmanntexas; 12-12-2019 at 07:39 PM.

    2012 Camaro SS/RS, LS3, m6, Whipple 2.9L, custom cam, E85, methanol
    2007 Avalanche, 5.3L "383", 2.3L Whipple, E85, custom cam

  2. #2
    Senior Tuner mbray01's Avatar
    Join Date
    Dec 2013
    Location
    Slidell, La.
    Posts
    1,015
    You likely have an issue in the second gear servo, or a broken accumulator piston. Its commanding second gear, just doesnt shift, then goes straight to third when its commanded.
    Michael Bray
    Rusty Knuckle Garage
    Slidell, Louisiana
    20yr Master Tech.
    Advanced Level Specialist
    Custom Car Fabrication, Customization, High Performance.
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