I just bought a brand new 2021 Duramax Z71. There was someone else on the way to look at it and I had to act fast. All local dealers were selling them as soon as they came in. The dealer I bought it from was on a busy highway with a lot of noise. When I got it home I noticed a knocking noise. I took it to three local Chevy dealers and had mechanics listen to it. It is pretty loud and obvious but they would not say it was abnormal. To me this is unacceptable. I noticed there is even a bulletin about it online. This is a $70,000 plus vehicle. Come on GM. What are you going to do about this? There should be a recall or something. Sounds like I'm not the only one unhappy about this.