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Thread: 6L90E shifting very early, doesnt match any shift schedule

  1. #1
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    6L90E shifting very early, doesnt match any shift schedule

    I've attached my current tune file and a scan of a WOT street pull. The car spins through 2nd after the 1-2 shift and I'm not sure if that is what is causing this (if I got WOT from a rolling start, same extremely early shift points)

    Car is shifting VERY early compared to the commanded RPM AND MPH. I have ALL shift schedules matching in the tune trying to figure this out.

    Transmission is out of a HD truck (fleet vehicle/box truck I was told)
    Stock converter
    NA 408 420/420 on the dyno
    Vehicle speed is correct/verified
    Trans torque is verified via logging/comparing on dynoStreet WOT test 5.hplRound 2.hpt

  2. #2
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    Looking at the logs more, the car is switching from "normal WOT" back to "normal" when it starts to short shift. Can't seem to figure out what is causing it though

    Adjusted the VSS by 30% and it changed the WOT shift rpm by 3%

    OS: 24265260
    Last edited by N3mi5is; 07-09-2019 at 08:02 AM.

  3. #3
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    Anyone have any idea???

    Continued to mess with the tune, the main culprit (which I can't figure out why) is car will show Normal WOT shift mode on log, run through a gear (4th on the highway for example) about 10 mph before it shifts, it will change to "normal" shift mode and then shift 4-5 and then immediately 5-6 with throttle still at 100%, VSS at 100 (4-5 commanded at 112 and 5-6 at 150).

    About to just swap TCM's

  4. #4
    Do you have logs that contain spark, airflow and cylinder air mass? your trans torque is really jagged and that looks to be causing issues with your shifts, on the one-two change at about 3.56 you can see the spikes in PCS4.
    2010 GXP Maloo ute, LS3, 6L80E.
    MM heads, 240/252@50 solid cam, 12.75:1 compression, 4500 Dominator converter, 3.46 rears.
    Shooting for 10s eventually.

  5. #5
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    Swapped to a CTSV T43/valvebody and full flashed a corvette OS 24243170 and that cured my issues.

  6. #6
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    Bringing this back up.
    With new afformentioned OS the WOT issue is resolved, but the part throttle shift scheduling DOES NOT change with TPS. When going WOT the shift mode change and it shifts correctly via WOT tables. But, for example, at 35% throttle or 70% throttle it will shift at the same MPH but a quicker/firmer shift from the higher torque. This T43 is getting the CAN data from my ProEFI ecu. All pertinent engine data reads correctly logging with HP.

    Could this be a bug in the OS?
    The ONLY thing I can find is if I use the polling tps channel (shows sae) it reads a constant 35%. The broadcast channel reads accurately.

  7. #7
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    Quote Originally Posted by N3mi5is View Post
    Bringing this back up.
    With new afformentioned OS the WOT issue is resolved, but the part throttle shift scheduling DOES NOT change with TPS. When going WOT the shift mode change and it shifts correctly via WOT tables. But, for example, at 35% throttle or 70% throttle it will shift at the same MPH but a quicker/firmer shift from the higher torque. This T43 is getting the CAN data from my ProEFI ecu. All pertinent engine data reads correctly logging with HP.

    Could this be a bug in the OS?
    The ONLY thing I can find is if I use the polling tps channel (shows sae) it reads a constant 35%. The broadcast channel reads accurately.
    If it's what I think it is, check your "Safety Shift" tables, and make sure they are set the same as your pattern a/b tables.. I fought an issue that sounds exactly like yours for the longest time before I looked at these tables.

    I could also be completely off track.

  8. #8
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    Bringing this back up in case anyone has any insight.

    I've attached the current tune and a log. I've tried multiple different operating systems at this point (ctsv, corvette, camaro) all with the same symptom. I'm wondering if I possibly have an issue with the T43? It responds to all tuning changes but does not shift under the normal tables based off of throttle position but it WILL go into WOT shift mode which makes no sense.

    To answer the above, the safety shifts do match my normal shift tables.TCM revival drive 1.hplTCM revival 2.hpt

  9. #9
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    if you using the pro-efi, is it possible it's sending the wrong data to the transmission.

  10. #10
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    Quote Originally Posted by Tre-Cool View Post
    if you using the pro-efi, is it possible it's sending the wrong data to the transmission.
    Definitely possible. But all the channels I can log from the T43 with HP read correctly.

    Only discrepancy I have found is the TPS channel. The broadcast channel reads accurately all the time. The polling TPS channel reads when engine is not running, whenever engine is running it will read 34.9%.

    Also to note, while monitoring the CAN data, all pertinent TPS channels read the same engine off and engine running, so I’m not sure why HPT reads the polling channel incorrectly with engine running.
    Last edited by N3mi5is; 12-19-2020 at 04:42 PM.