Chapter 12 Driveline and Wheel Components 257
Wheel Bearings
The wheel bearings form a low-friction connection
between the rotating wheels and the stationary vehicle. All
wheel bearings are antifriction bearings. Antifriction
bearings consist of three basic parts: the inner race, the
rolling element, and the outer race. See Figure 12-18. The
rolling elements rotate between the two races, allowing the
races to move in relation to each other with a minimum of
friction. The rolling action also draws lubricant between
the moving parts. The rolling elements and races are made
of heat-treated steel for maximum durability.
The clearances between the parts of an antifriction
bearing must be tight enough to prevent unwanted move-
ment and vibration. However, the clearances must be loose
enough to keep friction at a minimum, allow lubricant to
enter between the moving parts, and compensate for
expansion as bearing temperature increases.
Other parts of antifriction bearings include the
bearing cage, which keeps the individual rolling elements
separated as they turn, and seals or shields, which keep
lubricant in and dirt and water out.
Drive plane
Cage
Inner race
Drive
Driven
Driven plane
Outer race
Bisecting plane
Figure 12-12. The balls in a Rzeppa joint operate in a bisecting
plane between the angles of the axle shafts. As the joint
revolves, the position of the balls will change so they remain in
this bisecting plane. The position of the balls is controlled by
elongated openings in the cage. (AC Delco)
Needle rollers
Trunnion
Housing
Shaft
(axle)
C-clip
Spider
Balls
Grooves
Figure 12-13. Exploded view of a tripod constant velocity joint.
(AC Delco)
Spider plane
Housing
Drive
Driven
Spider
assembly
Figure 12-14. Tripod joint operation. The tripod joint uses three
balls on needle bearings to transmit torque between the spider
(splined to the axle shaft) and the housing. As the joint revolves,
the three balls will change their positions to stay in the same
plane as the spider. The balls can move in and out of the hous-
ing to allow for length changes as the suspension travels up and
down. (AC Delco)
Boot
clamp
Boot
Boot
Boot
clamp
Boot clamp
Boot clamp
Drive shaft
Differential side Wheel side
Figure 12-15. A cutaway of a rear drive shaft showing the
CV boots and clamps. (Lexus)
Needle bearing
Bearing cap
Seal
Cross
Needle
bearing
Seal
Bearing cap
Retaining clip
Drive shaft
yoke
Figure 12-16. A Cardan universal joint assembly. (Dodge)