The most common locking differential is the limited-
slip differential. One type uses clutch packs placed
between the side gears and the differential case. Friction
discs are splined to the side gears; steel plates are dogged
to the case. The clutch packs are pressed together by the
pressure of the spider gears on the side gears.
When the vehicle is moving straight ahead, the limited-
slip differential operates like a standard differential. The
rear axle parts turn at the same speed, and the clutch packs
are not used. When a wheel starts slipping, the difference
in pressure on the side gears causes the clutches to apply.
The difference in traction between the inner and outer
wheels is not a factor during normal turns, and the friction
discs and steel plates slip over each other.
Another version of the limited-slip differential uses
cones instead of clutch packs. Operation is similar to the
clutch-plate differential.
The ratchet differential has a series of internal cams and
ramps that direct power to the wheel with the most traction.
Its operation depends on relative wheel speeds, rather than
wheel traction. The ratchet differential transfers power
through a set of teeth, which can be engaged and disengaged.
The Torsen differential uses an arrangement of worms
(drive gears) and worm wheels (driven gears) to transfer
power. On turns or when one wheel is slipping, the axle
gear and worm wheel arrangement transfers power from
the faster wheel to the slower wheel.
The rear axle housing encloses and supports the other
parts of the rear axle assembly and forms a reservoir for the
rear end lubricant. The rear brake assemblies are usually
attached to the rear axle housing. The rear axle housing is
attached to the vehicle body by the suspension system.
Two kinds of rear axle housings are used on vehicles
without independent rear suspensions. The removable carrier
type has all of its moving parts, except the axles, in a carrier
Chapter 16 Rear Axle Assembly Construction and Operation 331
Brake disc rear
Wheel bearing
Stub axle
Axle oil seal
Rear wheel hub
Disc shroud
Brake
carrier plate
Spacer
tube
Roller
bearing
Oil seal
Rear drive axle
(central shaft)
Shock absorber
Cardan U-joint
Dust
cap
Gasket ring
Control arm left
Figure 16-39. This shows how a stub axle and universal joint of an independently suspended drive axle are installed to a hub and
wheel of a vehicle with an independent rear suspension. (Porsche)