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Thread: 07 Sububan 4l80e swap downshifts to neutral.

  1. #1
    Potential Tuner
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    Sep 2022
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    07 Sububan 4l80e swap downshifts to neutral.

    hello everybody
    i have a 07 suburban that i have swapped out the 4l60 for an 02 2500hd 4l80.
    The 4l80 had 325k miles on it so I decided to rebuild it before I installed it.
    internal duel feed and all the drill mods and harness repin on sloppy
    https://sites.google.com/site/sloppy...80e-info?pli=1
    sonnax performance pack
    https://www.sonnax.com/parts/5460-performance-pack
    sonnax clutch over run kit
    https://www.sonnax.com/parts/4496-sm...utch-valve-kit
    pioneer master rebuild kit
    full bushing kit
    new billet single disk TC
    did a matching OS T42 "segment" swap from an 07 suburban 2500.

    truck seem to run great and feels great with all up shifts 1-2,2-3,3-4, and 4th lock up.
    and when you're in any gear and floor it for the downshift to a lower gear to accelerate feels like it goes to neutral and RPM just rises.
    called Sonnax to ask there techs if they had any idea what would cause this mechanically, and they said they didn't have any ideas and thought it might be a programming problem.

    the only other symptom i have is sometimes is that reverse sometimes has delayed engagement /
    please let me know if you have any ideas
    will try and get a line pressure driving and shifting in the next few days
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  2. #2
    Senior Tuner blindsquirrel's Avatar
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    Since '07 Suburban 4L80E is a combo that was actually built at the factory, I think the OE diagrams/pinouts would be a more reliable source to use...

    Pinouts:
    Document ID 1757960.pdf
    Document ID 1735742.pdf
    "A country man between two lawyers is like a fish between two cats."
    check out my YouTube channel! 'Performance Motorsports Media Studios Productions FULL-SEND Barn Find Fabrication Lifestyle Garage'

  3. #3
    Senior Tuner blindsquirrel's Avatar
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    "A country man between two lawyers is like a fish between two cats."
    check out my YouTube channel! 'Performance Motorsports Media Studios Productions FULL-SEND Barn Find Fabrication Lifestyle Garage'

  4. #4
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    I’ll double check the pin outs

    I would think I’d get some sort of check engine light

  5. #5
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    double checked all my wiring and it is all correct.
    i did use bluecats trans tool and it seemed to help my downshift.

    do it seems programing and not mechanical.

    any idea that i change from the original that helped
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