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Thread: random delayed 2nd to 3rd shift

  1. #1
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    random delayed 2nd to 3rd shift

    Jeep GC 2016 srt8
    zf8spd

    I have a random delayed 2nd to 3rd shift , generally after coming to rest say at a light .
    Its more evident when cold but will still arise randomly when at normal running temps ,

    where it would normally change at about 1500 eng rpm under 20 % throttle or less on the odd occasion it will run as high as 2700 rpm, unless I reduce acc and then it will shift

    I have been chasing this for months tried various shift schedule changes and Tcc lock up variations which have improved various areas but the underling random behaviour 2/3 remains

    Any thoughts would be appreciated !

  2. #2
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    Post ur trans tune...it will be in there somewhere.
    Flat road or on an incline?

  3. #3
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    HemiTuna will spot it if there's something off. He's helped me learn a lot about the ZF8

  4. #4
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    Do you have anything on the RAM EcoDiesel 8HP70?

  5. #5
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    Never messed with one. These transmissions are pretty complex though. Seems like about every time you make it shift faster you're back to readjusting everything else to keep it from slipping or shifting too hard.

  6. #6
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    Quote Originally Posted by ridenrunwv View Post
    Never messed with one. These transmissions are pretty complex though. Seems like about every time you make it shift faster you're back to readjusting everything else to keep it from slipping or shifting too hard.
    Make sure you are using the latest beta.

    This trans has a ton of settings that can't be seen in older versions.

    Amazing trans when tuned well!

  7. #7
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    181026 1304 new jeep os adj fly tq softer.hpt

    Hi ,HT

    Thank you for your reply
    I hope the tune appears above , Have not done this before and Im a little unsure of whats req
    the odd behaviour 2/3 shift happens on flat road and to a lesser extent effects 3/4 as well
    I do have a tcm logging problem HP is looking at , Currently I cant identify what map number its using or tcm map nos ,,, I used to be able to but there is some break blocking the data stream..

  8. #8
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    What trans mode when it does this??

  9. #9
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    Quote Originally Posted by Hemituna View Post
    What trans mode when it does this??
    Normal mode , I will have a look see if I have a good log that shows it
    Nige

  10. #10
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    I'd hazard a guess it is the TCC.
    Your 2/3 shift at 20% and less is rather close to the converter lock up speed.
    Try lowering the lock up speeds and/or also the converter slip % especially if you have more tq than stock.
    Last edited by Hemituna; 10-29-2018 at 05:07 AM.

  11. #11
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    Ok
    Yes does have more tq ,, procharger F1a 12+ psi max


    However when it does delay it does not feel like its slipping and is above lock up by quite a bit ,,That has been an approach Ive been exploring as you can see,, but perhaps not far enough ?,The car is much better to drive with my current Tcc revisions ,

    If HP can fix my logging problems perhaps I can get some useful data covering the problem event and when its OK,,
    Q
    Converter slip % , That's the new set 0f 70 odd tables isn't it ?

    Thanks heaps

  12. #12
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    Q
    Converter slip % , That's the new set 0f 70 odd tables isn't it ?

    Sure is.

  13. #13
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    Quote Originally Posted by Nigel Pitsch View Post
    Jeep GC 2016 srt8
    zf8spd

    I have a random delayed 2nd to 3rd shift , generally after coming to rest say at a light .
    Its more evident when cold but will still arise randomly when at normal running temps ,

    where it would normally change at about 1500 eng rpm under 20 % throttle or less on the odd occasion it will run as high as 2700 rpm, unless I reduce acc and then it will shift

    I have been chasing this for months tried various shift schedule changes and Tcc lock up variations which have improved various areas but the underling random behaviour 2/3 remains

    Any thoughts would be appreciated !
    Look at shift scheduling, table 5 under aggression 0. The problem is that your 2>3 and 4>3 are 425 at low throttle. Raise the 4>3 downshift rpms so the transmission isn't trying to shift up, down, down, up....basically. raise.PNG
    Last edited by Spooby; 12-08-2018 at 07:38 PM.

  14. #14
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    Quote Originally Posted by Spooby View Post
    Look at shift scheduling, table 5 under aggression 0. The problem is that your 2>3 and 4>3 are 425 at low throttle. Raise the 4>3 downshift rpms so the transmission isn't trying to shift up, down, down, up....basically. raise.PNG
    Sorry I have been busy so bit slow to reply, !!

    Thanks for looking !! I will have a look at that ,
    You will probably have seen I have overwritten all the aggression 0 and 1 maps..

    What gets me is 70 % of the time its very nice and I like the feel of it,, the car has quite a bit of TQ and does not need to rev to get moving ,, but ill try your suggestion see if behaviour is improved
    Thanks
    N

  15. #15
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    PS it does it 2>3 upshift mostly and these shift numbers are not close