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Thread: 4L80 T42 problems

  1. #1
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    Question 4L80 T42 problems

    I'm fighting a problem with an 80e swap. Here are the details. Also, I do this for a living and have tuned quite a few vehicles for myself and customers.
    Also this isn't my first post. I couldn't get logged into my old account so after multiple tries I just created a new account.
    This is my first dive into the T42
    2007 Avalanche
    E38
    just rebuilt a 5.3, small cam and an On3 70mm turbo. Still working on the tune, but that will come once the trans is sorted out.

    T42 originally 4L60e (original T42 cal attached)

    swapped to an 80e that I rebuilt with a few mods.

    Wiring changed to match 80e and tune for an 80e with the same OS and Cal ID (cal I started with attached)

    I made a few changes to shift speed and RPM, but that's all. (cal also attached)

    On my first drives I only had 3rd, 4th, and a very harsh lockup. Did some checking and I had 2 pins unseated form the TCM connector. Disassembled it and got that fixed.
    Now it starts out in first if i drop it into manual low and goes through the gears manually. Come to a stop and have to go back through manually but no shifting in Drive.
    Pulled the trans out, tore it down completely, reassembled it. Air checked everything, tested the solenoids (all electronics and harness are new), so I know for sure the trans is good. Wiring between trans and controller continuity checks good.

    If someone with some expertise can take a look at the calibration to see if something is off that I'm not catching, I would greatly appreciate it.
    Attached Files Attached Files

  2. #2
    Joe (Moderator) joecar's Avatar
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    Can the TCM see VSS...?

  3. #3
    Joe (Moderator) joecar's Avatar
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    Where the the 4L80E tune come from (year/model/vehicle)...?

  4. #4
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    Try these files, I took the original 60e file and segment swapped just the Transmission and Transmission Diagnostics segments in from the 80e file. The System segment isn't mapped in EFILive, it may/may not need to be changed for the 80E swap (likely not), but may some code related to communication protocols. Especially with the base 80E file being from a Duramax Van, that could be part of it.

    If you're still experiencing the issue, can you post the ECM file as well? Hearing harsh shifting leads me to down the path of SD/failed MAF. Any hard starting or DTCs on the ECM side? I left the crank sensor unplugged once after dropping the oil pan, my truck started and ran, but went into failsafe mode and commanded max line pressure for the trans = really harsh shifts.

    What gears and tire sizes do you have on the truck? I'm thinking the speedo stuff is off, and speed input (hence Joe's question) is needed to shift.
    Attached Files Attached Files
    Last edited by ScarabEpic22; May 12th, 2021 at 07:34 AM.
    ~Erik~
    2013 Sonic RS Manual - 1.4L I4T E78, tuned, turbo mods, etc.
    2008 TrailBlazer SS 3SS AWD Summit White - LS2 E67/T42, bolt ons, suspension, etc.
    2002 Chevy TrailBlazer LT 4X4 Summit White - 4.2L I6 P10, lifted, wheels, etc.

  5. #5
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    Thank you guys for the replies.
    I finally got it to work but not without some headache. Every time I flashed the TCM I would be prompted to license it.
    Even after what showed as a successful flash it would still be the 60e file when I would read it. I still don't know what was going on but the full flash finally took.
    My theory is that my V2 may be going south. The serial port quit working last year and it may be time to upgrade.

    Thanks again for the help.

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