Whoop whoop whooping that 2020 Duramax does is annoying. What makes it worse is it doesn't start doing it until you have 500 to 1000 miles on the truck. If it did it during test drive, GM would have A LOT of trucks still on their lot. I traded in one with oil pump tick that was way better than this one with the hollow thumping. There is a GM bulletin out on the current issue and GM recommends doing nothing as this noise is "normal". Well if it's so "normal" why doesn't it do it from the first mile and not after you are "married" to it? They need to find a way to fix it or people will buy something different and GM will go belly up... again.