SummitSierra24

New here, but I have a 2021 GMC Sierra 1500 AT4 with the 5.3/10speed combo sitting at just about 67k miles. I was lucky enough to not have the notorious lifter failure (knock on wood) but I've also noticed the shudder whenever going from coasting to lightly accelerating to maintain speed, at any speed as mentioned here thanks to the lovely DFM system. I did test this by placing it in "Manual" mode and setting it to 9th gear being the highest gear and it did make a big difference in how smooth it was. The exhaust flapper valve issue is also taking place now and is a noticeable rattling sound whenever accelerating from 1,800 to 2,500 rpm when its warmer outside (65 degrees or warmer). It's pretty aggravating spending the amount we do on these trucks and them having countless issues. I purposely kept this truck bone stock and didn't modify it in any way, and maintained it as well as humanly possible. This truck hasn't even gone over 5,000 miles on each oil change with factory spec oils. Unfortunately yet again, there was never a straight answer given for any issues. The only other thing I experienced was a lower ball joint failure at approximately 62k miles which isn't normal either. That was a lovely bill, especially when I was advised that whenever the lower ball joint fails, the entire lower control arm assembly has to be replaced because it's a "non-serviceable" part and they can't replace just the ball joint. GM severely dropped the ball on this one and I've been a die hard GM fan for years. I wish I never got rid of my 2013 and just fixed the body rot issues. The only vehicle that I had a worse experience with, was a 2017 charger I bought new and kept for 2 years. But even then, it wasn't much worse than what is happening now. Come on GM, you're literally running us out of the company and forcing us to look at other options when considering trucks. Not all of us lease and dump these vehicles on the next person who doesn't know what they're getting in to.