GM 6L80 Transmission Information Thread

[CTX-SLPR]

From Sonnax:

That ball being missing very well could have played a factor in your symptoms. It is in the 1st gear circuit and was added to fix downshift complaints and engagement issues.

Those are pretty much my exact complaints so that's a good sign that I'm on the right track.

 

[CTX-SLPR]

So far so good, other than a brief scare when I hit the Trans Fast Learn button in HPTuners and I lost all gears things seem really good. I restored operation by just reflashing the TCU with the tune and the test drive was totally normal. Only thing I noticed was it felt a little soft going into top gear accelerating away from a light a moderate throttle but I don’t really remember how that was before.

Tomorrow I’ll go for a much longer drive to get the temp up to at least the 180’s and see if the 1st gear “overrun” on decel or delayed engagement pulling away come back.

 

[Doug118]

@NickTransmissions my 2008 6l80e operates perfectly when the trans temp is under 150°. The second temps on the gauge go over 150, I lose reverse, and 3rd and 5th gear slips like the truck is in neutral. As soon as they drop back below 150°, everything returns back to shifting smooth and all gears work. Is there something in the tcm that controls line pressure in those gears or something else electrical that could be wrong? It’s very odd that it can go from perfect to losing those gears back to perfectly fine within a 15 minute drive

Also, temps climb pretty rapidly if I sit idling for a few minutes. As soon as I drive, temps start to drop again