2020 2500 transmission slipping

[Blac]

My 2020 2500 has under 5k on it and the transmission started slipping while shifting on small inclines at low speeds. It happened all the sudden and was so bad that I had to pull over to allow cars to pass until I could pull into a parking lot and call my dealer. They told me to bring it in. I limped my way to the dealer 5 miles and had one of the service reps drive it  to verify that what I said was happening was actually happening.  When it slipped was during a gear shift and if you didn’t pay attention to it the rpm would peg out. I had to let off the gas allow the fine to idle down and ease on the pedal again. Anyone have any similar experiences?  Waiting on words from the dealer

[Ray Pickle]

Sorry to hear that. 21k so far and no issues here. Keep us updated on cause please.

[Njmurvin]

Deleted

Edited December 2, 2020 by Njmurvin
Sorry. Wrong forum.

[L8T]

So what did the dealer end up diagnosing it as? Did they fix the issue?

[Blac]

The dealer ended up ordering a transmission and replaced it with approval from GM. I have my truck back as of yesterday  and it moves better than when i turned it in so that’s is a good thing. I will let everyone know if things go bad again thanks for the interest

 

[SteveSr]

Hello was this accompanied with a loud clunk when downshifting in the lower gears?

[ug87]

My 21 Sierra SRW is in the shop for something similar. Put it into reverse to back into my driveway(slight hill) and it revved to over 4000 rpms and barely moved in reverse. Moved it through all the gears and let it sit and it did it again.  We'll see what the shop says. There was no noise, clunking, or smells.

[ug87]

So after changing the upper and lower valve bodies, they removed the transmission and disassembled it. They found some bad internal parts and are changing them, clutch housing, seals, and piston. 

[L8T]

Mine just started flaring the 2-3 shift on occasion. Hopefully that’s just a software fluke and not a hard parts failure on the horizon. 

[ug87]

They ended up having my truck over 5 weeks. They took the transmission out a second time and replaced more 4-5-6-R clutch parts. Not sure exactly what they replaced yet, waiting for all of the paperwork to be sent over. That's fixed it so far.