Whenever I put the truck in reverse as I let off the clutch a clunk/clattering noise can be heard in the front (sounds like on the center/passenger side). The noise continues even after the clutch is out. It also occaisonally happens randomly when not shifting gears. Any ideas what it could be?

Optional Information:
2001 Nissan Frontier V6 3.3L 4x4

Already Tried:
Check brakes