i drive a '03 6.o F250 and sometimes when i hit the brakes hard backing or forward i get a loud clunk in the rear. another thing i am curious about is this clunk i get in the front left over bumps, small or large. anybody have an answer or fix? i bought the truck a few thousand ago and it just slowly started this.
My '03 and lots of others have needed the sway bar bushings replaced. Bad bushings causes the rattles under there over the bumps. Do a search for sway bar in the super duty section and you will find lots of answers.
As for the clunk in the rear, could be an indication that the rear spline needs to be greased, another common problem with the SDs.