Had a 2017 Silverado 1500 2wd that did this and now my 2020 RST with < 200miles is doing it. Damn man, I should be on these forums looking for kick-ass mods I want to do. Instead, I'm in TROUBLESHOOTING! LAME. Anyway, on 2017, it was the leaf springs and all I had to do was put some rubber between the leafs and the noise went away completely and stayed away. Guess I'll have to apply this hack to my brand new, $50K truck or go to the dealer for that run-around. Sucks that its just so much easier to fix this crap yourself than to spend countless trips to the dealer when they should know exactly whats up with this by now. Hope you GM product guys are listening.