I have a rattle in the front of my 2003, I can't feel it, but I can hear it if I have the window down, and what it is, is the brake pads, I take them out and spread the tin slider bushing things so they fit tighter and that cures it for a couple of weeks, but it keeps coming back, it's almost embarassing, everytime I hit a little bump you can hear it rattle away.
2003 GMC Sierra Crew Cab 4x4, Bully Dog Dyno Dominator 90 hp, Bully Dog Power Pup 155 hp, Duramaximizer, FASS 150gph fuel pump, Bully Dog Trans, K&N Intake, Bully Dog 4\" dual exhaust, Flex-A-Lite electric replacement fans.