I've had my car to a Chevy dealership twice for this noise. The first time a sway bar link was replaced in the back. Still had the clunking noise, sounded like it was bottoming out. Went back a second time because it was in the front now and was told it was the bump stops doing there job. Still making noise but had a trusted technician ride with me to listen to it. He did figure it out. Can't believe it was only a small stone that got wedged in the front spring. No more clunking noise!