I had a banging noise when the vacuum axle disconnect system wasn't working properly. The collar wouldn't always connect the shafts properly and then bang and pop outta gear. Not really a snapping noise, but a noise that might help you eliminate something... Is it at all speeds/rpms? Does the snapping happen more when you speed up?
1992 4.0HO 5spd -- BDS 3.5" lift -- 33x11.5 M/T's -- Gibson Cat-Back -- 8.8 with 4.10's -GONE
1967 FJ, linked, 350 chevy, 35's, arbs, blah blah...
"If you're not moving ahead, you're falling behind"