Rear Axle

a group of subassemblies or a separate unit of a motor-vehicle chassis (such as an automobile and tractor) that transmits torque from the propellor shaft or directly from the gear box to the propelling mechanism.

In most motor vehicles the rear axle has a housing, tubes for the axle shafts, a final drive (including the differential with reduction gears), and the axle shafts. The final drive and axle shafts are part of the motor-vehicle transmission. Wheel brakes are mounted on the rear axle, as are the hubs for the wheels. The rear axle is joined to the frame or body of the motor vehicle (to the supporting body if the motor vehicle has no frame) by a suspension. When the rear wheels are independently suspended, the differential is attached directly to the frame of the motor vehicle, and in this case the pivoting axle shafts have ball-and-socket joints. The housing of the rear axle is a hollow supporting beam and is the axle of the automobile. The housings are cast of steel or malleable cast iron or are stamped and welded. The tubular casings of the axle shafts are pressed or welded into the housing of the rear axle and form a unit with it.

The rear axle housings can be made so they can be dismantled (vertically). A housing that can be dismantled consists of two parts joined by bolts. The final drive is in the middle, wide part of the housing. In a rear axle with a housing that cannot be dismantled, the final drive has a separate housing that is fastened by bolts to the middle part of the housing. The wide middle part of the housing reduces the road clearance of the motor vehicle and makes it necessary to increase the height of the floor. In order to decrease the dimensions of this part of the housing (which is especially important for heavyduty vehicles and for buses), the reduction gear of the final drive is made smaller by introducing additional, so-called wheel, gearing.