A transaxle is a single mechanical device which combines the functions of an automobile's transmission, axle, and differential into one integrated assembly. It can be produced in both manual and automatic versions.
Csonka transaxle from 1908
Drawing of the "Alfa Transaxle" layout, with gearbox mounted in block at the rear differential; also inboard brakes to reduce unsprung mass
An axle or axletree is a central shaft for a rotating wheel or gear. On wheeled vehicles, the axle may be fixed to the wheels, rotating with them, or fixed to the vehicle, with the wheels rotating around the axle. In the former case, bearings or bushings are provided at the mounting points where the axle is supported. In the latter case, a bearing or bushing sits inside a central hole in the wheel to allow the wheel or gear to rotate around the axle. Sometimes, especially on bicycles, the latter type of axle is referred to as a spindle.
Railroad car wheels affixed to a straight axle, limiting them to rotate in unison. This is called a wheelset.
A Denney axle
A 0 Series Shinkansen wheel used on Japanese high-speed bullet trains
Splines on a front drive axle