Chapter 12 Driveline and Wheel Components 255
Centrifugal force tends to throw lubricant out of a
CV joint. To keep grease from leaving the joint and protect
the joint from dirt and water, CV boots are installed over
the joint.
As the grease is thrown outward, it strikes the inner
cover of the boot. When the vehicle stops, the grease flows
back into the joint. The accordion pleats on the boot allow
the joint to move in and out as it compensates for changes
in axle length. CV boots are held in place by boot clamps.
Typical CV boots are shown in Figure 12-15.
Universal Joints
The universal joint, or U-joint, is used on drive shafts.
Sometimes U-joints are used on the transfer shaft of a front
drive axle. U-joints are often called cross-and-roller joints
or Cardan joints. The basic U-joint consists of a central
four-pointed cross, or spider, with caps that contain needle
bearings. The caps are attached to yokes on the drive shaft
and corresponding parts. As the drive shaft turns through
an angle, the cross twists within the caps. The needle
bearings reduce friction and vibration. A typical U-joint is
shown in Figure 12-16.
Intermediate shaft
Dust boot
Adjusting
nut
Center support
bearing
Snap ring
Dust deflector
Universal joint
Propeller shaft
Transmission
Nut
Adjusting washer
Nut
Mounting bolt
Differential
Propeller shaft assembly
Bolt
Figure 12-7. One type of two-piece drive shaft. Note the center support bearing. (Lexus)
Transmission
Slip yoke
Propeller shaft
Frame
Coil
spring
Bump
Propeller shaft
Frame
Transmission
Universal joints
A
B
Figure 12-8. The drive shaft (propeller shaft) must compensate
for changes in drive shaft angle. A—Normal operating angle.
B—A bump forces the differential upward. The angle has
changed, and drive shaft is shorter. A slip yoke permits this
change in length.