Sebrina, welcome to the forum. If you crawl under our C7 or look at it up on a lift, you will see that there are a number of brush guards underneath. If I had to guess, it sounds like you are getting some gravel underneath the guards as you go over these "speed bumps". The only thing that will get rid of that would be to get underneath and pop them off to get out the gravel. It doesn't sound like a mechanical issue.