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Thread: Strange shifting on A8 SS

  1. #1
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    Strange shifting on A8 SS

    Curious if anyone else has experienced this one. This started happening before my recent switch to E85 and a tune so I am sure it isn't that. The car was totally stock. After about 10,000 miles when it does a 1-2 shift or a 2-3 shift near red line but before fuel cutoff, it's like it loses a little power, shifts then picks right back up. It happens really quick but you can definitely feel it. Prior to that, the transition in power from one gear to the next was butter-smooth. It can be described as a "blurp" maybe. After tuning and E85, it still does it. I thought about valve float but I can't imagine a stock engine and cam doing that. I also considered spark plug flame out or ignition coils. I am at a loss. No engine codes are set. I would appreciate any insight.

  2. #2
    Senior Tuner Ben Charles's Avatar
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    Was the Tq model and coif changed under e85?
    Probably left stock

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  3. #3
    Advanced Tuner IARLLC's Avatar
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    I cannot really speak to why it is different than before but...

    Lots of people go to Spark>Advance>Minimum Spark>Base and Long Term and raise the minimum. Factory has the spark retarding to -30 at times. Some take the tables all of the way up to +10...power stays quite a bit stronger throughout the shift....and for my own car I would go that high (with some changes to the trans tune). For customers that want the trans to last a long time and don't want to pay to tune the trans I bring those tables up to just -10. It makes a very noticeable difference in the shift without increasing the stress too much on a stock trans/with stock tune.

    Give it a try. You can always go back to stock if you don't like it.

  4. #4
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    I'll check that out this weekend. Thank you!

    Ben - I don't know but I'll check!

  5. #5
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    http://gmauthority.com/blog/2019/04/...ission-defect/


    If it was doing it stock i would have to say its probably a hardware issue.

  6. #6
    Advanced Tuner IARLLC's Avatar
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    While GM has had enough issues with that trans...I have not seen that they relate to full throttle upshifts.

    There are a few changes that can be made to the trans tune that really help with the common issues (converter shutter, early light throttle 1-2 upshift, no throttle 3-1 downshift bang).

    Ben is totally right. If anything has been done to affect how much torque the engine produces and/or when it is produced......the trans will not be able to respond properly unless the torque model is corrected to match the motor's production.
    Last edited by IARLLC; 05-24-2019 at 03:53 PM.

  7. #7
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    Quote Originally Posted by ud03803 View Post
    Curious if anyone else has experienced this one. This started happening before my recent switch to E85 and a tune so I am sure it isn't that. The car was totally stock. After about 10,000 miles when it does a 1-2 shift or a 2-3 shift near red line but before fuel cutoff, it's like it loses a little power, shifts then picks right back up. It happens really quick but you can definitely feel it. Prior to that, the transition in power from one gear to the next was butter-smooth. It can be described as a "blurp" maybe. After tuning and E85, it still does it. I thought about valve float but I can't imagine a stock engine and cam doing that. I also considered spark plug flame out or ignition coils. I am at a loss. No engine codes are set. I would appreciate any insight.

  8. #8
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    I really appreciate your response. Any recommendations on doing that? Can that be done without the trans tune? I do plan to get the credits for the trans tune at some point, but have to feed the kids first. I am from the old school LS1Edit days with my long gone, but never forgotten 2000 408 SS so all this torque management is new to me. I'll also search the forum real good to see if I can find suggestions. Thanks again!

  9. #9
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    So here's my long term minimum. When you say take it to -10, do you mean every cell to -10 or 10 less than what is shown? If I am way off base, please put me in the right direction. Sorry to be the big newbie, trying to understand how these tables function. Is the one I posted here stock or did the tuner change it? Capture.PNG

    Also, it looks like the tuner modified these values in torque management. I guess those map to my drive modes.
    Capture2.PNG
    Last edited by ud03803; 05-28-2019 at 10:55 AM.

  10. #10
    Advanced Tuner IARLLC's Avatar
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    I am not sure how others do the base and long term minimum tables. I have seen that some just make the whole table 10 degrees or whatever they like. It seems to work fine for them. I just raise all settings to at least my minimum. If the window was already above what I want for a minimum then I leave it and smooth up to it.

    Yeah, looks like your tuner adjusted your DD (driver demand) tables. It is a quick way to increase the vehicle's reaction to the gas pedal but it needs to be done carefully on these GEN5s. Because it is based of speed and torque, any change in shift points or raised torque in the wrong spot really affects shifts and torque application. I do different things with these depending on the use of the vehicle. Some like to completely get rid of - numbers but then you won't have much if any engine braking. You might try returning those DD tables to stock just to see how it affects your strange shifting. You can always add it back in or blend them with stock tables to get what you want.

  11. #11
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    Thank you for the advice, I'll definitely try changing it back just to see.