02 f150 4x4 sport clunk

i am looking at buying an 02 f150 4x4. v-6 5-speed stick. the dealer let me take it overnight and i noticed that almost evry time you shift there is a clunk (most predominantly 1st to 2nd but noticable in all upshifts) as soon as you disengage the clutch. i dont think that it is the clutch itself because you can hit it as much as you want not in gear and its fine. there is some play in the rear axle. you can move the driveshaft a bit and here a some noise from the diff. so i guess my question is, is this common on these vehicles and has anyone had this problem before?

Check the U joints.