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Thread: 4L80E converter locking issue

  1. #1
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    4L80E converter locking issue

    I have a 4l80e in a supercharged silverado 6.0 previously equipped with a 4l60e. I drove it with the scanner on it and it does certainly act funny especially when you move the gear indicator and look at the commanded gear. It goes from P R N D 3 2 1 obviously but the commanded gear doesn't follow that pattern at all. Its all over the place.
    It also in low gear will kill the truck if you take your foot off the brake. (converter engaged) it drives "OK-sh" in D and 3 but the Converter locks way early and it shifts mega HARD as one would expect.

    I looked at the tune and it appears to look ok to me but Im very poor at looking at these things but Im learning...slowly. I'm going to attach the tune file and a log.
    The last time I had something stupid like this happen on another truck it was a botched segment swap.

    truck tune.hpt21-05-08 12-28-50.hpltruck tune.hpt21-05-08 12-28-50.hpl

  2. #2
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    All Im still struggling to determine if the issue that Im having is a botched tune or something else. Can someone help me determine what is happening in the shift speeds D1 and D2 these are set to zero. This doesnt make sense to me. What effects would this have? Instant shift when it sees mph in D1 and D2? Normally i would think these would be a max number.

    Another thing i can see when logging is tcc slip percent is always 80 percent wether or not its locked. RPM when locked is proper with no more than 5 rpm.

    I have 185psi trans pressure in the gauge in all drive gears. 230 in R


    I just cant figure this thing out[ log attached ATTACH]109783[/ATTACH]truck tune.hpt
    Attached Files Attached Files
    Last edited by Hazmatt; 05-12-2021 at 05:56 PM.

  3. #3
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    Did you rewire the main transmission harness for the 4L80E?

  4. #4
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    Yeah the truck has the adapt-o-harness on it so there wasnt any repinning required.

  5. #5
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    Quote Originally Posted by Hazmatt View Post
    Yeah the truck has the adapt-o-harness on it so there wasnt any repinning required.
    Some of the adapter type transmission harnesses don't require a segment swap at all. They will simply use the 4L60E calibration and change the solenoid outputs accordingly. Do you know who manufactured the adapter harness and the part number? If so, just reach out to them and see what needs to be done...if anything. You might simply be able to load the 4L60E tune back into the PCM.

  6. #6
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    Quote Originally Posted by kevin87turbot View Post
    Some of the adapter type transmission harnesses don't require a segment swap at all. They will simply use the 4L60E calibration and change the solenoid outputs accordingly. Do you know who manufactured the adapter harness and the part number? If so, just reach out to them and see what needs to be done...if anything. You might simply be able to load the 4L60E tune back into the PCM.
    This harness was a nelson performance harness requiring tuning.

  7. #7
    Senior Tuner Frost's Avatar
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    Just start over again with new, different, OEM files. Do your segment swap. Move your other tune data back in with compare. If this is someone else's tune, you should be doing this from the beginning, and as policy.
    Steve Williams
    TunedbyFrost.com


  8. #8
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    Thanks for confirming my thoughts Frost. Last night the stupidest of things happened with the truck we noticed tow haul only works in D3 put heres the kicker it neutrals 3rd gear but 1 and 2 work. Turn the button off all gears work again. *shake my head* thanks all for the help i will post back when i get it corrected.