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Thread: 4l60e GMC Sierra not shifting

  1. #1
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    4l60e GMC Sierra not shifting

    Hi I have a 1999 GMC Sierra 4.8 4l60e and I?m having a problem where it won?t shift when I give it full throttle. When it gets to about 5,600 rpm?s it just bangs on the heat and won?t drop into the next gear. I recently got myself a mpvi3 to try to fix this problem myself any help would be useful thanks !
    Last edited by Alex13____; 04-25-2023 at 07:30 AM.

  2. #2
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    If you read the tune off and get a datalog of the issue it would be most helpful.

    I've seen these issues caused by poor tuning, bad transmission, or low transmission fluid level.

  3. #3
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    I will do that thank you ! I think it?s a bad tune the guy that tuned it for me retuned it twice and still the same issue with less banging in between shifts

  4. #4
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    It could be bad tuning.

    It can also be low on fluid. Several 4LXX platforms like a TBSS specifically will start missing shifts just half a quart low on fluid.
    Tuner at PCMofnc.com
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  5. #5
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    Will check that once I?m home but I don?t think it?s that. I broke 2 transmission because of that problem both were checked a good amount of times & it didn?t do it till after I got it tuned

  6. #6
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    Are you sure the dipstick tube is seated all the way in the trans?
    100% sure the dipstick is giving you an accurate reading?

  7. #7
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    Quote Originally Posted by Alex13____ View Post
    Will check that once I?m home but I don?t think it?s that. I broke 2 transmission because of that problem both were checked a good amount of times & it didn?t do it till after I got it tuned
    WHat happened with the previous 2 transmissions?

  8. #8
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    Just checked and all is good on oils ���� And both other transmissions just stopped going into gear it would just rev on drive and reverse and not move.

  9. #9
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    Sounds like pump failures?