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Thread: Help with logging 6T70 shift issues

  1. #1
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    Help with logging 6T70 shift issues

    I'm hoping someone on the forum here might be interested in helping analyze transmission logs / provide feedback

    I'm not sure about what I should be logging - any help here would be great. If there are some guides please link them, I like details, feel free to explain things in detail.

    I posted this question over on the VCM Scanner forum a week ago, but got no replies.


    Back story:

    I have a 2013 Impala with the LFX engine and 6T70 transmission. Bought the car a couple years ago with 42k miles, trans fluid was dark, had it flushed by a reputable transmission shop, and I can confirm they put the right fluid in - Dex VI (synthetic).

    Issue 1) Under light acceleration from a stop, I can feel several short hesitations, best I can tell this occurs in 3rd gear. It feels like the transmission is preparing or starting to shift and then doesn't, 3, 4 or several attempts later it will complete the shift.

    Issue 2) 3rd to 4th is sometimes a hard shift - often after issue 1 above has been occurring, and if I have accelerated moderately to hard then lifted off before 3rd to 4th shift - e.g. winding up to 35 to 45mph quickly to merge in traffic from a stop.

    Both issues do not happen with moderate to heavy acceleration, everything is normal. But will also occur if I have gone from moderate to heavy acceleration, then lifted off the accelerator to light throttle or coasting.

    If I disconnect the battery to clear anything learned, transmission performs nicely, with less "slop" in the shifts until the adaptives are set/learned again and the issues come back. Quite honestly I think the car performs and drives better before the adaptives are set - everything feels tight, responsive and on-point, which seems backwards to me.
    Last edited by Weasel; 09-23-2018 at 10:45 AM.
    --
    2013 Impala LTZ. 3.6 LFX.
    2002 Impala LS. 3800 Series II, OverKill 91 Tune, Shift Kit, Allison TES 295 fluid, BRISK GOR17LGS Plugs.

  2. #2
    Tuner ZeroBoostBuick's Avatar
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    In my opinion it's 1 of 3 different things (or 2 of 3 things )

    1. Fluid level too high
    2. Fluid level too low
    3. Shit fluid that doesn't hold proper viscosity when warmed up.

    Here is a video that shows how to check the fluid level on GM's Dipstick-less transaxles...

    https://www.youtube.com/watch?v=WPGwvwrGPlc&t=325s

  3. #3
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    Did you figure out what it was? I?m having the same issue

  4. #4
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    Except mine only does it 1 time when you first start off. Doesnt matter if its hot or cold, it does the several short hesitations like you said like its preparing to shift but doesnt and at first I thought it kinda felt like a misfire but its only happening in 3rd gear. And after it does it that one time I guess the computer conpensates for it and it doesnt do it again until you turn the car off and back on again. Its doing all the same things you decribe except it only does it that one time and Im assuming the adaptive transmission is compensating for it and thats why it doesnt do it again until the next drive cycle, the fluid is in good shape and correct level and Im at a total loss diagnosing this problem
    Last edited by Tylerxx1234; 10-12-2019 at 07:25 AM.

  5. #5
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    Quote Originally Posted by Tylerxx1234 View Post
    Except mine only does it 1 time when you first start off. Doesnt matter if its hot or cold, it does the several short hesitations like you said like its preparing to shift but doesnt and at first I thought it kinda felt like a misfire but its only happening in 3rd gear. And after it does it that one time I guess the computer conpensates for it and it doesnt do it again until you turn the car off and back on again. Its doing all the same things you deceive except it only does it that one time and Im assuming the addaptive transmission is compensating for it and that?s why it doesnt do it again until the next drive cycle, the fluid is in good shape and correct level and I?m at a total loss diagnosing this problem
    Last edited by Tylerxx1234; 10-12-2019 at 07:23 AM.