So this thread is pretty depressing to read. I am the new owner of a 2018 Sierra Denali with a 6.2. Bought it new as a leftover with 300 miles on it 2 weeks agog I have almost 600 on it and have made a laundry list of issues for the dealer to tackle. One of them being a significant vibration/shake at highway speeds and the front outer edge of the tires look like shit, you can feel the chop in them if you run your hand over them. Bridgestone A/T. To get this much chop in less than 600 miles means the alignment has to be out pretty significantly. I traded in my 03 Sierra Crew quadrasteer that drove like a dream.....yes, second thoughts are upon me. I don’t drive the truck much, less than 5k a year but I shouldn’t be having these issues with a brand new $66k vehicle. I’ll keep you posted for dealer solutions to my list. I am open to ideas but I will start with alignment, rotation, tire balance for the vibration.