Can't figure this sound out
 

My cousin has a 03 WG and noticed a weird sound coming from the top of transfer case while riding. It is more obvious when the bike isnt running but rolling the bike back and forth, it sounds like a piece of plastic is riding on top of a gear or something? Remember when you were a kid and put a playing card in the spokes to get that cool sound? Sounds like that but not near as loud. We got a service manual and will tear into it but wanted to get some idea beforehand. Anyone else experience this problem or even if it is a problem? Thanks for any input

anyone?