I had a 2016 Silverado crew Z71 4x4 and it was smooth as glass til I was in an accident this spring when the truck had 28000 on it. To replace it I got a 2016 Sierra slt all terrain double cab and it has the shakes. Oddly enough, I have it around 42-48 mph then again at 75+. I'd be thrilled with the truck if it didn't have the slower speed shake. I never drive that fast lol. I had a PICO scope done and the dealer told me they have a truck on the lot (brand new) that shook worse. Going to take it back in and kindly ask them to check again with me on the ride so I can make sure I'm satisfied with their test. If it shakes worse I'll have them road force balance the tires and go from there to get it smoothed out.