Types of live rear axles
There are three types of live rear axles: Semifloating, three quarter floating and full floating. Let us see the details of these.
Semi floating axle:
The semifloating rear axle is shown in the diagram The short rear axle shaft inner end is supported only be the differential side gear. The differential case carries the inner bearing between it and the axle shaft housing that supports it. The inner end of the axle shaft is thus relieved of the task of supporting the weight of the vehicle. The weight of the vehicle is supported by the axle housing. Now the outer end of the axle supports the weight of the vehicle and takes up end thrust. Hence, this construction is called Semi floating rear axle.
The inner en of the axle shaft is splined to the differential side gear. The outer end is flanged and the wheel is bolted directly to it. In some designs, the hub of the wheel is keyed to the outer end of the axle shaft. The axle housing supports the wheel bearing, which is placed inside the outer end of the axle housing. The bearing is held on the axle by a retainer. The bearing is held on the axle by a retainer. Most axle bearings are prelubricated. With this arrangement, the brake drum, the wheel, and the bearings retainer plate must be removed in order to withdraw the axle shaft. This arrangement results in the axle shaft helping to support the weight of the vehicle in addition to transmitting rotation to the wheels.
Three quarter floating axle:
The three quarter floating axle is shown in picture In this axle, the wheel hub is supported by the single bearing located in the center of the wheel hub. The wheel hub runs on the axle housing. The axle shaft is keyed rigidly to the wheel hub. This arrangement provides the driving connection and maintains the alignment of the wheel.
The construction at the inner end of the axle shaft is the same as with the semi floating type. This axle is not supported by bearings at either end. The three quarter floating axle has only one bearing at the outer end. It is not as quite as the full floating type.
Full floating axle :
The full floating axle is shown in diagram In this axle, the wheel hub is supported by two bearings. The bearings are running directly upon the axle housing. The axle shaft is fastened to the wheel hub flange by means of a coupling. Through the coupling, the rotary motion of the axle shaft is transmitted to the hub and wheel. With this arrangement, the axle shaft can be removed from the housing without disturbing the wheel by removing the hub cap and the coupling.
In the full floating axle, the axle shaft is not supported at either end by bearings. The position of the axle shaft is maintained by the way that it is supported at both ends. As such, the axle is relieved of all strain caused by the weight of the vehicle or end thrusts. Now, the only function of the axle shaft is to transmit the rotary motion or torque to the wheel. Because of this fact, the axle is called full floating.
Full floating axle is the only construction that holds the wheel in position even when the axle shaft breaks. In other types, the wheel comes off and causes the vehicle to drop. The full floating axle is used almost exclusively in trucks.
In all applications, in axle construction either tapered roller or ball bearings are used.