my 01 has been making this annoying rattling sound except when I brake. It's not taking away performance from the way the truck is driving, & you cant hear it w/ the windows up. But it's always there. What could it be? something loose or should I replace something. please tell me before I take my truck apart!

 

if you hit the brakes &the rattling stops its most likley the missing anti rattle clips on the front brake pads