Results 1 to 5 of 5

Thread: Having Issues with 4L80E Shifting

  1. #1
    Advanced Tuner
    Join Date
    Jan 2006
    Posts
    299

    Having Issues with 4L80E Shifting

    Vehicle is a 1972 K10 with a 408" with LS3 heads.

    Hardware:
    - 0411 ECU
    - Painless harness (converted to 80E wiring at trans)
    - 4wd 4L80E
    - Front VSS installed
    - Rear VSS using a Novak Analog to Digital Signwave generator (8k pulses per mile) from the T-case

    Symptom
    - Truck will not shift on it's own
    - Truck shifts to every gear when forced via VCM controls
    - It will do 1-2 right away if you manually shift it but I believe that is do to the 2nd gear start option for icy conditions

    Software
    - Engine tune was from a stock file that I have modified
    - Trans segment swap was done from a same OS but for a 2500HD

    What I have tried
    - Stock shift calibrations loaded in to this tune from various 2000-2002 Chevy HD trucks
    - I have tried 3 PCM's with this tune

    Additional info:
    - Speed reading in HP tuners is calibrated accurately with in 1-2mph via GPS
    - I notice in some places the speed wavers or oscillates in the log file. I feel this would lead to erratic shifting behavior, not a no shift condition (see 4:00 - 4:34). I bring this up as someone else might spot it.
    - Examples of placed it should have shifted
    * 1:15
    * 1:36
    * 2:13 - 2:22 (I moved the shifter to 2nd at 2:22 to force the 1-2 shift)

    Basically any time you see an upshift in this log from it was either forced via this shifter (1-2) or VCM controls.


    Any help would be great.
    Attached Files Attached Files

  2. #2
    Advanced Tuner kingtal0n's Avatar
    Join Date
    Feb 2017
    Location
    miami
    Posts
    839
    I cant look at your files on this computer but if you are getting a speed while in neutral or see the speed oscillating there is a chance you've got the 2 VSS sensors connected backwards.

  3. #3
    Advanced Tuner
    Join Date
    Jan 2006
    Posts
    299
    VSS are wired correctly, no mph unless rolling. I have even disconnected the front VSS (it technically is not needed).

  4. #4
    really hop you figure it out man, im in the same boat and already thinking of swapping out to something else
    mine wont shift at WOT. thought i had it resolved but man its a pain.

  5. #5
    Advanced Tuner kingtal0n's Avatar
    Join Date
    Feb 2017
    Location
    miami
    Posts
    839
    The wot shifts need to be commanded way before the shift occurs.

    The computer tells the trans to shift at say 5000rpm but it's internal hydraulics dont actually move and fill recesses with fluids until say 5800rpm.

    It depends how fast the vehicle is accelerating. With say 1000rwhp you would command a 6500rpm shift at say 5500rpm. With 200hp you could tell it 6300 and it will only reach 6500 by the time it shifts because of slow acceleration.


    It also depends on line pressure, make sure you commanding for 4l80e a full line pressure at WOT of 180psi to 200psi verify with the gauge on the pressure port.
    Use torque management to protect the trans and limit tire spin issues and hard shifting which result with excess sprag wear.
    Never use D4 "fourth gear" for 4l80e when the trans is shifting 1-2 or 2-3 or the roller clutch will take a beating and probably shatter at some point.

    Now for the op, I see you've got some kind of conversion converter box on the output of one of the VSS and that you seem to be having trouble with the shift points related to that output... coincidence?