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6l80/90 shift issue exploration

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I've had a rash of those transmissions with problems.  Found a couple vids for info.  Gonna spend a few hours to see if I can diagnose/repair these things before they burn up clutches.



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Yep! For high HP cars, the tune has to be spot on or they die fast.

If the TEHCM is bad, i.e., hesitating, slamming gears, or like mine and the TC solenoid locked the converter, it'll break the 6L's quick as well.

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  • 2 weeks later...

My brother and I are kinda combining forces on this issue.  Yesterday he put in a new Trans Go TCC valve and Sonnax seal kit in a 6l80.   Said performance was good afterward. 

Sonnax does have lots of "fixes" for 6L80/90s, mostly in the valve body.

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My TQ Converter still feels like it's in lock-up.

I never had that TC issue until I swapped to the CTSV 6L90.

That said...

I gave Tim King all the parts I had to rebuild everything!

Hoping it doesn't do the same crap again and break because I'm so sick of trans problems!

Swear I'll sale it and move on to a new ZL1.







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On 5/19/2022 at 3:36 PM, Ashley P said:

Oh, and I fixed the ATF temperature on a 8Lwhatever it was....by replacing the harness on the valve body.  p0711

What did the harness have to do with over heating?

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