Rear ахles and differentials

The differential is a part of the rear-axle housing assembly, which includes the differential, rear axles, wheels, and bearings. As was previously explained, a differential is required to com­pensate for the difference the rear wheels travel when the car rounds a turn. If a right-angle turn were made with the inner-rear wheel turning on a 20 feet radius, it would travel about thirty-one feet, while the outer rear wheel would travel about thirty-nine feet. The differential permits application of power to both rear wheels while allowing the wheels to turn different amounts, when the car is rounding a curve.

There may be bevel differential which use bevel wheels and spur differentials which utilize spur wheels.

This secures additional gear reduction through the diffe­rential and thus provides a higher gear ratio between the double -reduction differentials.

In this type of differential the pinion meshes with a ring gear assembled to a shaft on which there is a reduction drive-gear set. The reduction drive-gear set drives a driven-gear set that has a greater number of gear teeth. Gear reduction is thus obtained between the drive pinion and the ring gear and also between the two reduction-gear sets. The driven gear set is attached to the differential case, with the case being supported bу bearings in the differential housing.

Types of rear axle. There are two basic types of axles: dead axles and live axles. The dead axle does not rotate; the wheel rotates on it. A common example is the axle on a horse-drawn wagon. Live axles are attached to the wheel so that both the wheel and the axle rotate together. Live axles are of three general types. They are classified according to the manner in which they are supported; semi-floating, three-quarter floating, and full-floating.

In the semi-floating axle, the wheel end of the axle is supported by a bearing in the axle housing. The differential end of the axle is splined into the differential side gear. The side gear and the axle are both supported by the differential case, which in its turn is supported by bearings in the differential housing. The differential end of the axle can thus be said to " float" since it is not directly supporting car weight. The wheel end of the shaft not only transmits driving movement to the wheel but also supports the car weight and resists bonding movement from side thrust when the car rounds a curve or skids.

In the three-quarter floating axle, the differential end of the axle floats, as in the semi-floating axle. The wheel end of the axle is attached to the wheel hub, and the wheel is supported by a bearing on the outside of the axle housing. This relieves the axle shaft of the car weight, since this weight is carried through the bearing on the axle housing. The shaft is merely required to transmit the driving torque and resist bending movements from side thrust when the car turns skids. In the full-floating axle, the differential end of the axle floats, as in the other types of axles described above.

The wheel end of the axle is attached to the wheel hub with the wheel being supported by bearings placed on the out­side of the axle-housing in a manner similar to that used in the three quarter floating axle. There is difference between two bearings (usually roller bearings) which support the wheel on the axle housing. The bearings carry the load and also keep, the wheel in alignment thus relieving the axle of both these jobs. The axle has but one job to perform, and that is to transmit the driving torque to the wheel. This type of axle is used in heavy-dute applications where large loads are carried.