differential side bearing mounts have a provision for
adjusting the side bearing preload. This adjustment is
usually made with a threaded end cap, or adjusting nut.
The end cap is tightened against the bearing cup until the
proper preload is attained.
Drain and fill plugs may be mounted on the differen-
tial carrier or on the rear axle housing, depending on the
particular manufacturer. The ribs on the front of the carrier
strengthen it without adding a great deal of weight to the
assembly.
Integral Carrier
The integral carrier, as the name implies, is an inte-
gral part of the rear axle housing. See Figure 16-30. This
type of rear axle housing has a sheet metal or cast metal
inspection cover, sometimes called the differential cover.
The inspection cover can be removed to service the rear
end components. Service operations must be performed
under the vehicle, since the carrier cannot be separated
from the rest of the rear axle housing.
Figure 16-31 shows a typical integral carrier. Notice
that almost all the rear end components are installed inside
the rear axle housing. Most of these can be removed
through the opening that is kept closed off by the inspec-
tion cover. The cover is sealed with a gasket of some sort.
The pinion front and rear bearing cups are pressed
into the carrier portion of the rear axle housing. Integral
carriers do not normally have a pinion pilot bearing.
Differential side bearings are installed in the integral
carrier in the same manner as on a removable carrier. The
side bearing preload adjustment is sometimes made with
shims. These shims are placed between the bearing cup
and the rear axle housing. In other instances, the preload
adjustment is made with a threaded end cap, as on the
removable carrier.
Rear Axle Housing: Independent
Rear Suspension
On vehicles having independent rear suspensions, a
modified rear axle housing is used. Figure 16-32 shows
such a housing. Notice that the housing has no axle tubes.
The drive axles resemble drive shaft assemblies to some
degree, complete with conventional or constant-velocity
universal joints. This design allows each wheel to react
independently to the road surface, improving ride quality
and handling.
The housing has oil seals to prevent oil loss where the
axles enter the housing. The internal construction of the
housing is identical to the previously discussed carriers. To
reduce vibration and strengthen the drive train, a torque
tube is sometimes used to attach the front of the housing to
one of the vehicle crossmembers. (Torque tubes were
explained in Chapter 12.)
Rear Drive Axles
The rear drive axles transfer power from the differen-
tial assembly to the rear wheels. There are two major kinds
of drive axle designs. One is the solid drive axle, shown in
Figure 16-33; the other is the independently suspended
drive axle, shown in Figure 16-34.
Solid Drive Axle
A solid drive axle, or live axle, is a hardened-steel
shaft. See Figure 16-35. Each rear axle assembly in solid-
axle rear suspension systems has two. External splines on
the inboard (inner) end of each axle mate with internal
splines on the differential side gear to which it is connected.
An axle flange at the outboard (outer) end of each axle acts
as a wheel hub. It provides the mounting surface for the
brake drum or rotor and the wheel. The brake assembly and
wheel are installed directly on the flange wheel studs.
Each shaft is supported on the outboard end by an
axle bearing, also called a wheel bearing. The axle
Chapter 16 Rear Axle Assembly Construction and Operation 325
Pinion bearing Carrier
Side bearing
Side bearing bore Carrier
mounting flange
Bearing bore
Figure 16-29. The mounting flange of a removable carrier is
designed to seat against the axle portion of the rear axle
housing. The carrier is attached with studs and nuts. The
gasket is always installed between the carrier and the axle
housing. (Subaru)
Axle tube
Drive pinion
gear
Rear axle
housing
Ring
gear
Gasket surface
Inspection cover
Integral carrier
Figure 16-30. The rear axle housing with an integral carrier is
essentially a one-piece unit. All moving parts are inside the
housing. The differential parts are reached for service by
removing the inspection cover at the rear. This type of axle is
usually serviced under the vehicle.