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Thread: 2007 trailblazer 4.2 l6..4L60e swap to 4l80e

  1. #1
    Potential Tuner
    Join Date
    May 2021

    2007 trailblazer 4.2 l6..4L60e swap to 4l80e

    I need some help with my tranny i changed a new transmission 4l80e and the original one is 4l60e i did the wirings but still need to change in ecu.but still car stuck in 1st gear
    I paid hptuner to try to do changes with it . But have no option to do that
    Need some help with that ..
    Paid help or free help or someone to point me in the right direction
    Thank u all

  2. #2
    Advanced Tuner
    Join Date
    May 2006
    Seattle, WA
    I've not heard of anyone swapping an 80E into a non-V8 TrailBlazer until now, so seems like a cool project!

    There is no transmission segment (nor OS) compatible with your 2007 P12 PCM that will run a 4L80E, the P12 was only used with the 4L60E-family and manual transmissions. If you had an 08-09, this would be easy as there are compatible TCM OS' available. Upgrading to an 08 ECM+TCM isn't possible as the crank/cam reluctors on the I6s are different between 07 and 08.

    You will need to either:
    1) Repin the harness and add relays to run the 80E on the 60E transmission segment.
    2) Purchase a relay harness (not a normal swap harness) that is designed to run a 80e on 60e programming. Multiple vendors provide them, I know PCMofNC, TunedbyFrost, and others make them.

    Tire size/shift points/pressures/so forth can be done using HPTuners.

    You may also need to retune for the 80e ratios, it appears these are not mapped in the 07 TrailBlazer P12 file I have that uses OS 12627885. This may cause Traction Control, StabiliTrak, and/or ABS issues.
    2013 Sonic RS - manual, CGM, 6M, sunroof, mods in process
    2008 TrailBlazer 3SS AWD LS2, loaded, dropped, modded, SE22 Performance tuned. And then some...
    2002 TrailBlazer LT 4WD 4.2L I6, lifted, tires, exhaust, SE22 Performance tuned