Offroad-Express

on the way home the other night i heard a little bang and now i can hear a grinding noise when i let my foot off the gas. seems to be getting worse and worser. i cant really tell if its my gear box or my diff. how can i tell???

Jack it up and place on axles stands.
Then slowly work through the drive line turning each of the wheels and listening for noises. You will soon learn if it is front or back or G/box transfer case related.