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Thread: 4l80e upshifting when held in gear

  1. #41
    Senior Member Wolfie's Avatar
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    Thanks Taz. I've made all the tow/haul normal tables the same....
    Then as it's too damn cold out to have the laptop in the vehicle...
    I make changes to the tow/haul, try it out, and if it feels good, copy it over to the normal and make more changes to the tow/haul... Thanks for the offer, but all I have now that it's too cold to be building bikes, is play with the van. So I keep plugging away... It's getting there, but I was worried about too much pressure...
    Wolfie
    LS1B 2007 Express 6.0 /w 470,000+ miles (parked as of 01April2011)

  2. #42
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    I replaced the pressure control solenoid today and checked line pressure, It made about 65 at idle and 160-225 while driving but the shifts have not changed. Anything else I can look at??

  3. #43
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    Did you try the tune in post #37 ? If it doesn't shift firmly with that tune, then you have a real problem

  4. #44
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    Yeah, thats the tune I have in it now. Could it be that the VE tables are off as stated earlier?

  5. #45
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    Unless the VE is underestimating by a great deal (say 50%), then the shifts should have firmed up with that tune.

    My point about VE in post # 22, and Joecar's comment in post # 31, was that unless the VE table is reasonably accurate, the torque labels of the individual cells of the shift pressure table do not necessarily reflect actual torque output.

    This just means that you would have to adjust shift pressure by feel, or how the individual vehicle responded, rather than with respect to a proposed magnitude of torque output.

    As a test, you could set the 3>4 and 2>3 shifts to 96 PSI in all cells - if the transmission still does not shift very firmly - then it is doubtful the issue is in the tune.
    Last edited by Taz; February 1st, 2014 at 08:46 PM.

  6. #46
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    What about torque reduction? Should they all be 0's too? Mine is showing in the 20's above 207 ftlbs. Im almost at the point of pulling the trans out and having it checked out. I really appreciate you guys helping me.

  7. #47
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    With or without TR, increased shift pressure = firmer shifts. I never run any tune with zero TR. To satisfy yourself try it every way you can think of, but it is beginning to look like a mechanical issue of some sort.

  8. #48
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    I am going to put a pressure gauge on it today to see what it is actually doing. What should i log to see what it is actually doing vs. what is being commanded. Isn't there a way to measure slip %?

  9. #49
    Joe (Moderator) joecar's Avatar
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    Some things to log:
    MAF
    MAP
    TP
    VSS
    RPM
    TIS
    TOS
    TRQENG
    TFMPRS
    GEAR
    TCCMODE
    TCCDC
    TCCSLIP
    SHIFTLAST
    SHIFTERROR
    TFT
    ECT

    To observe internal slippage, compare TIS and TOS; to observe TCC slip, comapare RPM and TIS.

    For the 4L80E, when in 4th gear, TIS and RPM will be different since TIS is measured after the overdrive gearset.

  10. #50
    Joe (Moderator) joecar's Avatar
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    Quote Originally Posted by joecar View Post
    ...
    For the 4L80E, when in 4th gear, TIS and RPM will be different since TIS is measured after the overdrive gearset.
    In 4th gear, RPM and TIS will be in the ratio 0.75:1.

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