Rear Drive Axle Description and Operation 11 Inch Axle

Rear Axle Description

The Dana 11 inch ring gear axle uses a conventional ring and pinion gear set to transmit the driving force of the engine to the rear wheels. The gear set transfers the driving force at a 90 degree angle from the propeller shaft to the axle shafts.

This axle is full-floating. The wheel hubs support the axle shaft at the wheel ends. The shaft at the wheel end is supported and splined to the hub inner-diameter. The differential supports the other splined end of the shaft.

Two tapered roller bearings support the pinion gear. Underneath the inner pinion bearing cup, an oil baffle is installed to promote better lubrication. Also underneath the inner pinion bearing cup, the pinion position shims are located which are use to set the pinion depth. A shim pack at the front of the axle housing between the bearing cone and pinion gear sets the pinion bearing preload.

The ring gear bolts to the differential case.

Two tapered rolling bearings support the differential case. The differential side bearing preload is controlled by a 0.76 mm (0.030 in) hardened shim and a selective outboard spacer shim. The location of the hardened shim is between each differential bearing cone and the differential case. The location of the selective outboard spacer shim is between each differential bearing cup and the housing.

Rear Axle Operation

A basic differential has a set of 4 gears. Two are side gears and 2 are pinion gears. Some differentials have more than 2 pinion gears. Each side gear is splined to an axle shaft; so each axle shaft turns when its side gear rotates.

The pinion gears are mounted on a differential pinion shaft, and the gears are free to rotate on this shaft. The pinion shaft is fitted into a bore in the differential case and is at right angles to the axle shafts.

Power is transmitted through the differential as follows: the drive pinion rotates the ring gear. The gear, being bolted to the differential case, rotates the case. The differential pinion, as it rotates with the case, forces the pinion gears against the side gears. When both wheels have equal traction, the pinion gears do not rotate on the pinion shaft because the input force on the pinion gear is equally divided between the two side gears. Therefore, the pinion gears revolve with the pinion shaft, but do not rotate around the shaft itself. The side gears, being splined to the axle shafts and in mesh with the pinion gears, rotate the axle shafts.

If a vehicle were always driven in a straight line, the ring and pinion gears would be sufficient. The axle shaft could then be solidly attached to the ring gear and both driving wheels would turn at equal speed.

However, if it became necessary to turn a corner, the tires would scuff and slide because the outside wheel would travel further than the inside wheel. To prevent tire scuffing and sliding, the differential allows the axle shafts to rotate at different speeds.

When the vehicle turns a corner, the inner wheel turns slower than the out wheel and slows its rear axle side gear; as the shaft is splined to the side gear). the rear axle pinion gears will roll around the slowed rear axle side gear, driving the rear axle side gear and wheel faster.