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Any Chevy 6L80 trans experts?

Discussion in 'General' started by GRH, May 14, 2023.

  1. GRH

    GRH Well-Known Member

    I'm working on a 6L80 that's in a 2018 Silverado 4.3L with 125k miles, mostly highway. Friends vehicle. The trans has a rough shift after it warms up. It's also got a shudder. Code is P0777. Looking online suggests replacing the solenoid pressure switch films so I dropped the pan and removed the valve body to access the TEHCM. There is no metal in the pan so I'm thinking the torque converter is ok. Removal of the TEHCM showed the orange switch diaphrams are ok after I removed them. The solenoids all have consistent measurements of .8 ohms closed and 12k ohms open. At this point I'm scratching my head on what else to look at?

    Trans1.jpg Trans2.jpg Trans3.jpg Trans4.jpg
    Last edited: May 14, 2023
  2. ChemGuy

    ChemGuy Harden The F%@# Up!

  3. skidooboy

    skidooboy supermotojunkie

  4. AndyR1

    AndyR1 Well-Known Member

    Mine had a shudder. Ended up being just a failing torque converter.
    cpettit likes this.
  5. GRH

    GRH Well-Known Member

    Did you end up having the entire transmission replaced/rebuilt ?
  6. cpettit

    cpettit Well-Known Member

    I’ve seen a couple with that same problem/solution
  7. AndyR1

    AndyR1 Well-Known Member

    Just replaced the torque converter.
    Mine had a little shudder and I drove it for a long time. It progressively got worse. I paid a shop to drop the trans and just replace the tq. Then I dropped the pan to clean it and put in a new filter. Pan had a lot of debris. New fluid. Drives just fine.
    I tow a boat 3,500lbs and toy hauler 6,900 lbs dry.
  8. 88/532

    88/532 Simply Antagonistical

    The 6L80 has had a variety of issues. The major one was the weak torque converter. The fix was installing a 6L90 converter, but even that wasn’t foolproof. Also, there is a spring in the valve body that breaks and causes the shuddering issues. Lots of info out there on those transmissions and their problems. And btw, there is a 26 state lawsuit against GM on the 6L90s from 2015-19. My 16 Sierra has one of those.
    VFR#52 likes this.
  9. sheepofblue

    sheepofblue Well-Known Member

    On my 2000 that code also says it can be fluid. At 125K that could be an issue though on mine it occasionally slam shift rather than shudders. Another thing to try is run tow/haul mode and see if it changes things.
  10. 88/532

    88/532 Simply Antagonistical

    Added a couple of videos in the youstube thread on these transmissions.
  11. GRH

    GRH Well-Known Member

    Thanks, I did watch those, that guy really knows his stuff
    Given the discoloration of the fluid in this unit and AndyR1's reply I'm changing my tune on it not being the converter to it being the issue since it wasn't the pressure films being broken.
    Seems like these transmissions have alot of weaknesses

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