i have an 02 f-150 4x4, and for about a month i've had either a very loud clicking/clapping sound or a clunk coming from the rear end. it seems limited to when i'm either pulling away from a stop or slowing down. however, these noises are not regular and don't always present themselves. i admit that i'm stumped, so if there are any suggestions out there i'd appreciate it. thanks

 

You don't happen to have an aftermarket exhaust, do you? If so, is it/could it beslapping up against somehting back there?