So I have a 2017 Sierra 1500, with the 6.2L and 8spd transmission. For the last couple of years, I've had an issue where there are hard shifts (mostly 1st to 2nd) or occasionally while towing on the highway as well. More chronic is when I'm driving, usually the first 2 or 3 stops in the morning I feel like I'm getting bumped from behind. A thunk with the truck being knocked forward. That part has been getting worse where it's not just the first 2 or 3, but more sporadic now as well.
I've brought it in a couple times and been told that they don't notice the issue, or hooked it up to something and everything is "within spec". They did change the tranny valve body or something a while back as well, but no fix, and getting worse.
Anyone had something similar? Any fixes advice? Warranty is up in Sept so would love to get it solved before then. I got it going in for an oil change on Monday, so bringing it up with them again.
Thanks!