The five types of final-drive now in use on motor vehicles are stated by the author to be (a) the chain-and-sprocket, (b) the bevel-gear, (c) the worm-gear, (d) the double-reduction and (e) the internal-gear. The advantages of each type as emphasized by its maker are presented and commented upon, and the same procedure is followed with reference to their disadvantages.Following these comparisons of the different drives, which cover about the first third of the paper, the bearing loads and shaft stresses of typical semi-floating and full-floating axles are calculated for the conditions (a) maximum torque plus the normal radial-load on the wheel, (b) the wheel locked and skidding forward when the brakes are applied and (c) the wheel skidding sidewise while the truck is moving. A tabulation of the results obtained from the mathematical calculations is included. The author concludes from these results that, while the maximum shaft-stresses are practically the same in both designs, the shaft in the full-floating axle can be made lighter and that a higher factor of safety should be employed in the semi-floating axle since the bending stresses are continually reversed. As the bearing loads in the full-floating axle are considerably higher, a greater bending-moment is imposed on the axle housing, thus increasing the production cost of this axle because of the necessity for heavier bearings and axle housing.The last third of the paper is profusely illustrated with photographs and drawings of various types of rear axle. These include the rear axle of the Class B truck, as well as commercial examples of the worm drive, internal-gear-driven axles with load-carrying members of different sections, double-reduction axles and an example of a chain final-drive.