a mechanism used in motor vehicles to transfer and increase the torque from a drive shaft to a vehicle’s powered wheels and, consequently, to increase its tractive force.
An axle drive transmits the rotation of a drive shaft through an angle of 90° to semiaxles. Most axle drives employ single or double gears and pinions. In a single gear and pinion unit the rotation is transferred from a small bevel gear to a large one. In addition to the bevel gear and pinion, whose axles are mutually linked, some passenger vehicles and a number of trucks employ a hypoid gear. In a double gear and pinion unit the rotation is transmitted through two pairs of pinions: the rotation of a small bevel pinion is transmitted through a large bevel gear and on from a small cylindrical gear to a large cylindrical gear. A double gear and pinion unit may be used to obtain a high gear ratio from a comparatively small axle drive since two pairs of gears are meshed. Some trucks have more complex axle drive featuring two gear ratios and a mechanism for shifting between them.