Standard Rear Axle

Standard Rear Axle Assembly:

Rear Axle Assembly With Traction Control (Acceleration Slip Regulation):

GENERAL INFORMATION
The standard rear axle is a semi-floating hypoid rear axle in which the vehicle weight is carried on the rear axle housing (16). The rear axle is designed for use with an open driveline and coil springs. The rear axle has a hypoid type differential ring gear (20) with the centerline of the differential drive pinion gear (23) below the centerline of the differential ring gear (20).

All parts necessary to transmit power from the propeller shaft to the rear wheels and tires are enclosed in the rear axle housing (16). The rear axle housing cover (43) is bolted to the back of the rear axle housing (16) and is removable to permit service of the differential case without removing the entire axle from the vehicle.

A universal joint connects the rear end of the propeller shaft to the drive pinion gear yoke (3). The drive pinion gear yoke (3) has a splined end which fits over and drives the drive pinion gear (23). Two preloaded tapered drive pinion gear bearings (7 and 18) support Me drive pinion gear (23) in the rear axle housing (16). The races of the inner drive pinion gear, bearing (18) and the outer pinion gear bearing (7) are press fit in the rear axle housing (16). The inner drive pinion gear bearing (18) is press fit onto the drive pinion gear (23). The outer drive pinion gear bearing (7) combines a light press fit to a close sliding fit on the yoke end of the drive pinion gear. The races of the inner and outer drive pinion gear bearings (18 and 7) are pressed against shoulders recessed in the rear axle housing (16).

Tightening the drive pinion gear nut (1) compresses a collapsible drive pinion gear spacer (8) that bears against the outer drive pinion gear bearing (7) and a shoulder on the drive pinion gear (23). The drive pinion gear spacer (8) is used to enable automatic bearing preload adjustment and maintain a preload on both inner and outer drive pinion gear bearings (18 and 7). Adjustment of the fore-and-aft position of the drive pinion gear (23) is obtained by placing selective drive pinion gear shims (19) between the head of the drive pinion gear (23) and the inner drive pinion gear bearing (18).

The differential case (33) is one piece and is supported in the rear axle housing (16) by two differential side bearings (32). These are preloaded by inserting differential bearing shims (24) between the bearings (32) and the rear axle housing (16). The differential case (33) is positioned for proper differential ring gear-to-differential drive pinion gear backlash by varying the shim thickness from side to side. The differential ring gear (20) is bolted to the differential case (33).

Two left and right differential pinion gears (40) have splined bores for driving the axle shaft (63). They are positioned to turn in counterbored cavities in the differential case (33). The upper and lower differential pinion gears (40) have smooth bores and are held in position by a differential pinion gear shaft (35), mounted and locked in the differential case (33). All four gears are in mesh with each other. The upper and lower pinion gears turn freely on the pinion gear shaft (35), acting as idler gears when the rear wheels are turning at different speeds. The differential pinion gears are backed by differential pinion-thrust washers (37) and differential side gear thrust washers (38).

Vehicles equipped with the standard rear axle with the antilock brake system (ABS) have a rear wheel speed sensor reluctor wheel (39) press fit to the differential case (33). A wheel speed sensor (75) is bolted to the top of the rear axle housing (16). This sensor provides wheel speed information to the electronic brake control module (EBCM).

On vehicles equipped with the limited slip rear axle, ABS and traction control the rear wheel speed sensor reluctor wheels are an integral part of the rear axle shaft (63 or 70), and are not serviceable separately. The wheel speed sensor (75) is mounted to the rear brake caliper mounting plate (65), which is bolted to the rear axle shaft (63 or 70). This sensor provides wheel speed information to the EBCM. For further information on ABS with traction control refer to "BRAKES AND TRACTION CONTROL."

OPERATION
When the vehicle turns a corner, the differential allows the outer rear tire and wheel to turn faster than the inner tire and wheel. The inner tire and wheel, turning slower with respect to the outer tire and wheel, slows its (side) differential pinion gear (as the axle shaft is spliced to the side gear). The differential pinion gears roll around the slowed (side) differential pinion gear, driving the other differential pinion gear and tire and wheel faster.