STurner15

Never seen this issue before but... if you want a new head unit I have a Phoenix PX6 touchscreen for sale.

I have the same year, and engine so I already know exactly what type of "transmission" issues you're having... fun stuff with the 8speeds! Can't speak to the shocks and that issue but I have a set of 18" Denali wheels when you're ready

I just used my Diablo tuner. gears 1->2, and 2->3 I added +3 to the shift pressures.

so far so good on my end. added a couple pounds to low end gears shift pressures. smooth and solid still.

Got my letter in the mail and took it in immediately. 74k miles 6.2L. They flush the trans with new fluid and replace seals etc etc. have about 20-30miles on the truck now and it seems to run better. But I got a flush around 65k and it worked for a little while... so I am hoping this harness and flush works.... for a .. little while.... longer...

As everyone already mentioned, the dealership should/will flush the trans for free if its still under warranty, with the new "blue" fluid. My 6.2L 8 speed was at 65k ( out of warranty) when the shutter/slamming was happening at low end gears, took it to the dealer they flushed it under the new TSB that everyone is mentioning... made it a little better... for a little while, maybe 2-3k miles. So fast forward to 72k miles I got a letter from GM stating they have been having issues with their transmission temp sensor harness/connection and they would replace it for free if you've been experiencing the slamming/shuttering etc etc. The letter I got in the mail, the dealership references it as "doc# 5636702" and replacing this harness requires them to change out the fluids anyways. So if anyone is PAST their warranty, I would tell them you got this doc number in the mail and require the harness to be replaced. So far, after the new harness, it shifts extremely smooth. I only have maybe 15 miles on it.. so who knows, it could only last a couple thousand miles again. But this is a way to get a free flush if you're out of warranty.

Any luck here? Having the same issue with mine doing the MPH to Radio switch. The radio also just started randomly clicking things as well. Going to try to make sure the HMI is all tight but may include a battery unplug for 10min and see if that helps.

+1 Not great but I've seen a lot worse. Either way, while you have the opportunity get it cleaned up JL!