This type of U-joint is limited to use in light-duty,
vehicles. Other types of universal joints are used in the
axles of heavy-duty vehicles. The types you will
encounter in military designed vehicles are the Rzeppa
and Bendix-Weiss constant velocity joints (fig. 5-26).
The front drive axle of a four-wheel drive axle
requires locking hubs. Locking hubs transfer power
from the driving axles to the driving wheels on a four-
wheel drive vehicle. There are three basic types of
locking hubs, which are as follows:
MANUAL LOCKING HUBrequires the
operator to turn a latch on the hub to lock the hub
for four-wheel drive action.
AUTOMATIC LOCKING HUBhub locks
the front wheels to the axles when the operator
shifts into four-wheel drive.
FULL TIME HUBfront hubs are always
locked and drive the front wheels.
Manual and automatic locking hubs are the most
common. Used with part-time, four-wheel drive. they
enable the drive line to be in two-wheel drive for use on
dry pavement. The front wheels can turn without
turning the front axles. This allows for increased fuel
economy and reduces drive line wear.
FRONT-WHEEL DRIVE (AXLES)
Front-wheel drive axles, also called axle shafts or
front drive shafts, transfer power from the transaxle
differential to the hubs and wheel of a vehicle. Front-
wheel drive axles turn much slower than a drive shaft
for a rear-wheel drive vehicle. They turn about one
third slower. They are connected directly to the drive
wheels and do NOT have to act through the reduction
of the axle ring gear and pinion gears.
Front-wheel drive axles typically consists of the
INNER STUB SHAFTthe short shaft splined
to the side gears in the differential and connected
to the inner universal joint.
OUTER STUB SHAFTthe short shaft
connected to the outer universal joint and the
INTERCONNECTING SHAFTthe center
shaft that fits between the two universal joints.
Universal joints that connect the drive axle are
called CV joints. The outer CV joint is a FIXED
(nonsliding) ball and cage or Rzeppa-type joint that
transfers rotating power from the axle shaft to the hub
Figure 5-26.Constant velocity universal joints.
assembly. The inner CV joint is called a PLUNGING
(sliding) ball and housing or tripod-type joint that acts
like a slip joint in a drive shaft for a rear-wheel drive
The plunging action of the inner CV joint allows
for a change in distance between the transaxle and the
wheel hub. As the front wheels move up and down over
bumps in the road, the length of the drive axle (inner
joint) must change.
REAR AXLE SERVICE
Rear axle service is needed when an axle bearing is
noisy, when an axle is broken, bent, or damaged, or
when an axle seal is leaking. The rear axles must be
removed to allow removal and repair of the differential
Axle Bearing Service
Worn or damaged bearings in the carrier or on the
axles produce a CONSTANT whirring or humming
sound. These bearings, when bad, make about the same
sound whether accelerating, decelerating, or coasting.
When diagnosing and repairing bearing failures, do the
Check the general condition of all parts during
disassembly,, not just the most badly worn or