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4L80e in Hummer started slipping when warm....

Discussion in 'All Other Transmissions' started by Sand, Mar 28, 2018.

  1. Sand

    Sand Active Member

    187
    194
    Mar 27, 2016
    Canada
    Still picking low fruit - found a transmission service bulletin that suggested an optical sensor can create these symptoms.
    Un plugged it. Starts hard. Ran fine up to 110 deg then slipped.
    Looking at pricing the valve body kit. Any benefits to the HD version for me?
     
  2. Sand

    Sand Active Member

    187
    194
    Mar 27, 2016
    Canada
    And just for kicks I ruled out PMD by swapping in a good one.
     
  3. Sand

    Sand Active Member

    187
    194
    Mar 27, 2016
    Canada
    Would this work for diagnostic purposes to identify my issue before I do a rebuild?
    Screenshot_20180405-133736.png
     
  4. Sand

    Sand Active Member

    187
    194
    Mar 27, 2016
    Canada
    And rockauto has the shift kit too. Get the manifold and the kit to see what happens or just the kit?
    Screenshot_20180405-135551.png
     
  5. THEFERMANATOR

    THEFERMANATOR FRANKENBURBAN Staff Member Lead Moderator

    8,978
    2,302
    May 9, 2008
    ZEPHYRHILLS FL
    The pressure switch manifold is just a set of on off switches, and simply tells the ecm what gear is selected and the actual position of the shift valves. It doesn't measure actual pressure. And most shift kits do not include the pieces to fix the afl. The sonnax kit is roughly $45, but the tool set to install it is $300. I'm not sure how much the transgo kit costs with the reamer, but no kit to repair it is cheap because of the reamer cost.
     
  6. Sand

    Sand Active Member

    187
    194
    Mar 27, 2016
    Canada
    So this carries on...I pulled the trans and took it to pieces. Clean, beautiful, no real signs of wear or abuse. Clutches look great. Steels have no hotspots. Magnet was clean. Pistons are crack free. I threw in a transgo shift improver kit while it was apart and replaced the bushing on the oil pump end as it was the only one with some wear showing. I took the valve body to the trans shop and had them inspect the AFL. They said there was no scoring or wear.
    Good news for my transmission. Not as good for my issue. I replaced the internal wire harness as it seemed a reasonable precaution. Some of the wires going into the back of the plug had "wiggle" at the connector and some did not on the old harness. Ill put it back in tomorrow but I dont have high expectations. Im going to check all the external harness from the trans to the TCM today.
    Any thoughts while its all easily accessible are appreciated. 20180419_181627.jpg It was my first Auto transmission teardown/assembly. I did have fun
     
    MrMarty51 likes this.
  7. Sand

    Sand Active Member

    187
    194
    Mar 27, 2016
    Canada
    Im sooo bored of driving a campervan to work with tools and materials and jerry cans of diesel crammed in it....
     
    smokymtn65 and MrMarty51 like this.
  8. Sand

    Sand Active Member

    187
    194
    Mar 27, 2016
    Canada
    This just carried on too long with no results...
    I found a rebuilt trans with 1000kms on it that was behind an engine that got hydrolocked. I paid 700 bucks for it and threw it in. Works great. I dream of doing a post mortem on the old one but am happy just to move on. Thanks for the help everyone. My auto trans knowledge has grown hundredfold.
     
    Will L. likes this.

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