2017 GMC Sierra 1500 6.2L Transmission Hard Shifts/Clunks

[Eck21]

I have a 2017 GMC Sierra 1500 Denali 6.2L with the 8 speed transmission (73,000 miles). When shifting from park to drive/reverse there is a clunk and also when the truck is accelerating from low RPMs there’s a hard shift from 1-2 & 2-3 gear. I’ve taken it to the dealer multiple times and they “can’t find an issue” with it. Any help would be greatly appreciated!

 

Edited July 14, 2021 by Eck21
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[GC1009]

Longtime lurker, first time poster -

 

I've got a 2016 Yukon XL with the 6.2L. I was having a similar issue with a clunk when shifting out of park and have noticed what I describe as a hard shift or hesitation on occasion when shifting from 1-2 and 2-3.

 

The dealership said no issue with the transmission that they could find, but replaced the motor mounts - they are a piston/shock type assembly vs a rubber damper.

 

The motor mount replacement seems to have solved the clunk when shifting out of park, but the hard shift is still there. I've been looking for the TSB that talks about swapping out the transmission fluid multiple times if you're in a high humidity or coastal area as the fluid that was originally used apparently attracts moisture into the fluid. 

Edited July 25, 2021 by GC1009
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