I have a 2005 Chevy Z71, bought it new, got 82,000 on it now. At around 40,000 when I would hit the brakes the back end would jump up and down. Nothing violent, just aggravating. Figured it was the shocks, new Bilstiens all the way around, still had problem. Turned out to be warped front rotors. Installed a heavy duty set of new rotors and pads, problem gone. I was surprised that the original front pads still had a lot of life left. Might have gone 100,000 miles. Truck has original drum rears, bad idea GM.