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Thread: Trans Downshifting twice

  1. #1
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    Default Trans Downshifting twice

    I have put a 2001 6.0/4l80E in my 1993 Yukon. It is pretty much stock other than a cold air intake. My problem is while driving down the road and the trans is in 4th and in lock when I floor it the trnas shifts back to 3rd then in to 2nd. I am pretty sure I used a stock program, I just changed for my gears and tires and moved the shift points up a little. is it in my tune or do I have a internal trans problem?I have attached my latest .tun
    Thanks in advance.
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  2. #2
    Joe (Moderator) joecar's Avatar
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    Post some logs.

    If the PT 3->2 curve D0915 or WOT 3->2 MPH D0930 is met it will downshift to 2nd.

    Looking at your file, do this:
    - first, fix all the out of range values (not related to trans, but fix them).
    - set all the throttle kickdown tables D0960,D0961,D0962 to 100%.
    - each WOT upshift MPH D0910,D0915,D0920 must be above the correponding WOT downshift MPH D0925,D0930,D0935.

  3. #3
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    Thanks, I will mess with it when I get home.

  4. #4
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    How do you get rid of the out of range? I clicked on every one and they were set in range, I then saved the file then flashed the cal part of the file, and then I read it back and I still have out of ranges. do I need to do a full program?

  5. #5
    Joe (Moderator) joecar's Avatar
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    The tunetool displays the max allowed value for any parameter that exceeds the max... so it looks like it's in range.

    Do this, enter max-1 and save file, exit tunetool, re-enter tuntool, they should be in range now;
    if you really want max value, then enter max value, save file, exit tunetool, re-enter tunetool, and if they are all in range now do cal-only flash.

  6. #6
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    Ok got the out of range fixed, I changed D0960,D0961,D0962 to 100% and the WOT upshift MPH D0910,D0915,D0920 are above the correponding WOT downshift MPH D0925,D0930,D0935, but I still get a 4 to then 3 to 2 downshift. is it because D0930 is lower than D0915?
    I also ran a log and it shows 4 to 3 then 3 to 2.
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  7. #7
    Joe (Moderator) joecar's Avatar
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    Oh, are you saying on going WOT it goes 4->3 followed by 3->2 instead of 4->2...?
    (edit: hmmm.... takes about 1 second)

    I don't know why it does that.
    Last edited by joecar; October 13th, 2007 at 09:51 AM.

  8. #8
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    Yea, I am stummped. I would think it should go from 4 to 2. I wonder if it's an internal trans problem? I did just have it rebuilt.

  9. #9
    Joe (Moderator) joecar's Avatar
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    The GEAR pid is the commanded gear, and it is delayed... I think it's a PCM/tuning problem... for some reason the PCM is "loitering" in 3 on a WOT 4-2 shift... I don't think it's a trans internal problem.

    Does it do this when doing a part throtte 4-2 (i.e. at 45 MPH in 4th, go to 80% throttle)...?

  10. #10
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    you know I didnt pay attention to that, I only noticed it doing it under WOT. I dont think it does tho, I think it only jumps to 3rd, but I will drive it 2 morrow and let you know for sure.
    BTW, can I use the bi directional controls to force a 4 to 2 downshift? that way I know it's a pcm problem.

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