spaces produces pressure that can be used to operate the
other components of the differential assembly. Figure 16-24B
shows the operation of a rotor-type pump. Check valves
ensure that pressure is always produced, no matter what
the direction of pump rotation.
The internal gear is attached to one of the side axles.
The external gear is attached to the other side axle. When
both wheels have equal traction, both side axles turn at the
same speed. Therefore, the internal and external pump
gears do not move in relation to each other, and no pres-
sure is developed. When the vehicle loses traction to one
wheel, one of the side axles begins turning at a faster rate
than the other. The difference in axle speeds causes the
internal and external pump gears to move in relation to
each other, producing hydraulic pressure. This pressure is
delivered to the ring diaphragm, which expands against
the clutch pack. With the clutch pack applied, the side
axles lock together and turn as a unit. When the wheels
begin turning at the same speeds, the internal and external
gears do not move in relation to each other, and no pres-
sure is produced. With no pump pressure produced, the
ring diaphragm depressurizes and releases the clutches. If
one wheel again begins to slip, the pump starts operating
again, and the system reapplies the clutches.
When the vehicle makes a turn, the pump gears move
slightly in relation to each other. They do not, however, pro-
duce enough pressure to apply the clutches. Therefore, the
differential does not attempt to lock up during normal turns.
Some locking differentials are operated by an electric
motor attached to the axle assembly. Note the additional
parts installed on a standard rear axle, Figure 16-25. The shift
fork shaft and shift fork are operated by the motor and move
a hub sleeve. The hub sleeve has splines that can engage
matching splines on the differential carrier and side gear.
During normal non-locking operation, the shift fork shaft and
shift fork are positioned to keep the hub sleeve disengaged.
The hub sleeve has no effect on differential operation.
To lock the differential, the motor moves the shift fork
shaft and shift fork to engage the hub sleeve splines with the
splines on the differential carrier and side gear. The splines lock
the hub sleeve, differential carrier, and side gear into a single
unit. Locking the carrier and side gear together prevents the
other differential gears from turning. The differential assembly
turns as a unit, delivering equal power to each drive wheel.
Rear Axle Housing: Solid-Axle
Rear Suspension
The rear axle housing contains and supports other
parts of the rear axle assembly. It also forms a reservoir for
the rear end lubricant. The housing accommodates sus-
pension system attachment. Most rear axle housings also
support the stationary parts of the rear brake assemblies.
322 Manual Drive Trains and Axles
Housing
Outer
rotor
Inlet
Outlet
High
pressure
area
Inner rotor
Close fit seals
inlet and outlet
sides
Low
pressure
area
B
Figure 16-24. A—A hydraulic locking differential, consisting of a
pump with internal and external gears, a ring-shaped pressure
diaphragm, and a clutch pack. B—The arrangement of the
internal and external rotor resembles a rotor type engine oil
pump. The close fit of the inner and outer rotors forms a seal at
the point where the teeth almost touch in the pumping chamber.
(Daimler Chrysler)
A
Motor
Figure 16-25. Rear locking differential. (Toyota)