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Thread: 4L80 segment swap - No TC lockup, only on command

  1. #1
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    4L80 segment swap - No TC lockup, only on command

    Hi all,
    I recently purchased a 2006 Sierria 1500 that already had a swapped 4L80 that was not working. The 4L80 was swapped with the Michigan Motorsport swap harness and pins installed in the ECM. With the original tune the TC would not lockup unless commanded via HP tuners.

    Reading on here, I found you need to complete a segment swap with a vehicle of same year and OS. I uploaded and still not TC lockup, but still can command. I am stumped and do not know where to go from here.

    Can someone look at my tune and let me know if I am missing something?

    Stock 4l80 with same OS.hpt2006 gmc 4 door OG tune.hpt2006 gmc 4 door with STOCK 4L80 tune same OS.hpt

  2. #2
    Tuning Addict blindsquirrel's Avatar
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    Relay harness OR segment swap, not both together. The purpose of the harness is to make it work with the 60E segments. If you want to use the 80E segments instead you have to remove the adapter harness and wire everything as per the factory diagrams for a stock 80E truck.

  3. #3
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    Ive had issues with the swap harnesses. Just this year ive had 7 trucks that had lockup issues. Removed the swap harness and swapped the 2 pins in the 20 pin connector and fixed the issue.

  4. #4
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    Have you looked to make sure the brake switch is satisfied? You can log it normally under TCC stuff.
    Tuner at PCMofnc.com
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  5. #5
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    Quote Originally Posted by blindsquirrel View Post
    Relay harness OR segment swap, not both together. The purpose of the harness is to make it work with the 60E segments. If you want to use the 80E segments instead you have to remove the adapter harness and wire everything as per the factory diagrams for a stock 80E truck.
    Thank you for responding. So if I do not do the segment swap, do I sill change the Tranns Type to 4L80? Sounds like you are saying to change it back to 60E?

    Thanks again for your help.

  6. #6
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    Hi RDF1, thank you for replying. So if I remove the swap harness, do I sill need the two VSS signals to the ECM?

    Thaks for any input, just trying to correct what I jumped into.

  7. #7
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    Well, I tried to segment swap back to a 4L60 and it did not like it at all. Felt like it didn't want to move so I didn't push it and put my other tune back on. I am unsure if I just need to change the Transmission Style or actually segment swap back to 4L60?

    Next step is to remove the swap harness and re-pin I guess.

  8. #8
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    Quote Originally Posted by Alvin View Post
    Have you looked to make sure the brake switch is satisfied? You can log it normally under TCC stuff.
    I will have to look, not sure how to check this. Thanks for replying.

  9. #9
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    Quote Originally Posted by Houston Ben View Post
    Well, I tried to segment swap back to a 4L60 and it did not like it at all. Felt like it didn't want to move so I didn't push it and put my other tune back on. I am unsure if I just need to change the Transmission Style or actually segment swap back to 4L60?

    Next step is to remove the swap harness and re-pin I guess.
    With that harness you are going to need a 4l80 segment or TCM for later cars. We have a harness that does not require segment swaps or different TCM's. But this one you need the PCM or TCM programmed for a 4l80e.
    Tuner at PCMofnc.com
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  10. #10
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    Quote Originally Posted by RDF1 View Post
    Ive had issues with the swap harnesses. Just this year ive had 7 trucks that had lockup issues. Removed the swap harness and swapped the 2 pins in the 20 pin connector and fixed the issue.
    Feel free to email me the next time you run into this. It is a easy fix 99% of the time. [email protected]
    Tuner at PCMofnc.com
    Email tuning!!!, Mail order, Dyno tuning, Performance Parts, Electric Fan Kits, 4l80e swap harnesses, 6l80 -> 4l80e conversion harnesses, Installs

  11. #11
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    Thanks Alvin,
    I am using the 4L80 segment, but still won't lock up, only on command. Once back from vacation I will re-pin and see what happens.

  12. #12
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    Quote Originally Posted by Houston Ben View Post
    I will have to look, not sure how to check this. Thanks for replying.
    Yes it still needs the ISS and VSS.
    Also I've seen some have issues with the wrong speedo info.

  13. #13
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    Hi all,
    Back from vacation and got around to repining the 4L80 harness. I removed the white wire and moved the brown wire to the white wire's original location. However, this did not work and still no lockup.

    I think I am just going to take it somewhere. frustrated....

  14. #14
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    Also, almost every time I go to write, it fails to write and goes into reduce power mode. After a few attempts it will finally write. Is my ECM bad?

  15. #15
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    Quote Originally Posted by Alvin View Post
    Feel free to email me the next time you run into this. It is a easy fix 99% of the time. [email protected]
    Alvin, I sent you an email.