i have a D80 with 3.55 gearsi lucked into some humvee rims with beadlocks. they are 16.5x10.5 2 piece steelies. the smallest tire i can find is 33x12x16.5.i was thinking about going with a lower gear in the rear to help turn those beasts when i'm muddin(use the factories for highway). when they say "case split", what do they mean? are there 2 castings? they list some as "thin", is that what i need?thanks