It might be the notorious transfer case shifter rattle. Switch yourself to 2HI and lift up on your transfer case handle just enough so it's is tight and not bouncing around but not in 4HI position. If the rattle goes away or becomes not as bad then it's a good possibility you have a loose or worn out transfer case linkage components.
I hear that this is pretty common for jeeps. This is the cause of my rattle noise and unless I prop something under the transfer case handle to keep it in the "up" position while in 2HI, it sounds like something is bouncing around in a tin can.
http://www.jeepforum.com/forum/f9/adjust-tighten-transfer-case-linkage-465830/
I hear that this is pretty common for jeeps. This is the cause of my rattle noise and unless I prop something under the transfer case handle to keep it in the "up" position while in 2HI, it sounds like something is bouncing around in a tin can.
http://www.jeepforum.com/forum/f9/adjust-tighten-transfer-case-linkage-465830/