To elaborate a bit more -
Jeeps and many other axles have a cover on the back of the axle to get at the gears.
Toys, some fords, and a few other have the "3rd member" design where you unbolt 3rd member from the front of the axle (after removing the drive shaft). The 3rd member consists of the pinion, gear housing, and all the gears in one easy to work on package.
2002 KJ - staying stock (almost)
2000 TJ - 2" suspension lift, 1/2" body lift, assorted skids, hooks, rock rails, rock lights, 33" BFG MTs, custom bumper, Warn 8274 Mud Puppy's Jeep site