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Thread: 6L90E shuddering when converter locked and under load

  1. #1
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    Default 6L90E shuddering when converter locked and under load

    In 3rd or 4th gear under a load like when going up a decent hill, I can feel some shuddering or slipping of the torque converter. Is there something that can be adjusted to try to tune out the shudder or slipping or whatever might be going on?

    I see the ramp in D2216 and some TCC slip tables that I feel might be able to help some of this, but I'm not sure where I should start..

    Thanks

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    Any ideas? It's mainly in 5th when going up a grade. Feels like an engine miss, but it's only when the converter is locked

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    I feel like the converter is trying to hold on too long, like it shouldn't even be locked when it does this. Maybe I can figure out how to make it unlock sooner. TP% unlock maybe?

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    Joe (Moderator) joecar's Avatar
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    Is the ECM tune modified...? If so have the torque model tables been adjusted...?

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    Quote Originally Posted by joecar View Post
    Is the ECM tune modified...? If so have the torque model tables been adjusted...?
    Yes, the ECM is modified (PE delay, timing, other small things), and the torque model tables were increased by 15% I also decreased desired upshift times 10%

    However, this problem existed before I ever touched anything. Thinking about throwing in a bottle of instant-shudder fix.

    There is a TSB that I wish I could see, but apparently it's no longer available or expired.

    POWER TRAIN:AUTOMATIC TRANSMISSION
    Bulletin Number:
    09-07-30-001 Bulletin Date:
    Mar 2011
    Summary:
    GM: WHEN DRIVING AT HIGHWAY SPEEDS THERE MAY A SHUDDER OR BUCKING FEEL AT HIGHWAY SPEEDS. ( NHTSA ITEM NUMBER - 10038263 )

    Found the tsb here, with a guy that 100% accurately describes the problem I have http://community.cartalk.com/discuss...r-going-uphill

    I'd like to try increasing the TCC lock-up pressure (not the ramp-in) but it seems I can't figure out how to do that.

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    That particular TSB only applies to the 2 Mode Hybrid automatic transmission (M99) not the 6L80 (MYC) or 6L90 (MYD).

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    Quote Originally Posted by Taz View Post
    That particular TSB only applies to the 2 Mode Hybrid automatic transmission (M99) not the 6L80 (MYC) or 6L90 (MYD).
    Darn. Thanks Taz!

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    If it comes down to it, I will probably just try to unlock the converter at the specific speeds/TPS% conditions it's doing it under (it's very consistent!) but was hoping to find a fix in the tune rather than disabling a ... feature. I wonder if I can find a 2013/14 6L90e tune to see if the calibration is different or maybe improved in some way that avoids this issue.

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    Quote Originally Posted by Jim_PA View Post
    ... I'd like to try increasing the TCC lock-up pressure (not the ramp-in) but it seems I can't figure out how to do that ...
    Those parameters are not available in EFILive.

    Post your tunes, and perhaps I can help.

  10. #10
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    Quote Originally Posted by Taz View Post
    Those parameters are not available in EFILive.

    Post your tunes, and perhaps I can help.
    Ahhh -- OK! I don't know if those parameters would help or not, but it would be nice to bump up the pressure to see!

    Here are my stock and modified files. Thanks for offering to look! it's a 2010 Suburban 2500 LY6/6L90e (no AFM)


    2500burb_PE-timingAdj.ctz
    2500burb-ShiftSpeedReduced_TCCramp_inc.ctz
    2500burbStock.ctz
    2500burbStock-Trans.ctz

    Oh, and P.S. I have tried the self-clean and re-learn procedures, they didn't seem to do much.

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