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Thread: Help with logging 6T70 shift issues

  1. #1
    Potential Tuner
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    May 2018
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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; 3 Weeks Ago at 09:45 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
    Join Date
    Aug 2008
    Location
    S.W. Ontario Canada
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    125
    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