My 96 f-250 7.3 PSD is clunking when I start out from a stop. When I start out from a red light or stop sign, it seems that when the wheels get to a full revelution or 2 that a clunk is heard and felt. I am thinking U-joints or even motor mounts. My first and initial thought is motor mounts, because it is felt and seen from the hood. Any ideas of what it could be?