universal joint housing that positions the balls. When
both shafts are in line, that is, at an angle of 180
degrees, the balls lie in a plane that is 90 degrees to the
shafts. If the driving shaft remains in the original
position, any movement of the driven shaft will cause
the balls to move one half of the angular distance. For
example, when the driven shaft moves through an
angle of 20 degrees, the angle between the two shafts is
reduced to 160 degrees. The balls will move 10 degrees
in the same direction, and the angle between the
driving shaft and the plane in which the balls lie will be
reduced to 80 degrees. This action fulfills the
requirement that the balls lie in the plane that bisects
the angle of drive.
A tripod or ball and housing CV joint consists of a
spider, usually three balls, needle bearings, outer yoke,
and boot. The inner spider is splined to the axle shaft
with the needle bearings and three balls fitting around
the spider. The yoke then slides over the balls. Slots in
the yoke allow the balls to slide in and out and also
During operation, the axle shaft turns the spider
and ball assembly. The balls transfer power to the outer
housing. Since the outer housing is connected to the
axle stub shaft or hub, power is sent through the joint to
propel the vehicle.
CENTER SUPPORT BEARINGS
When two or more drive shafts are connected in
tandem, their alignment is maintained by a rubber
bushed center support bearing (fig. 5-10). The center
support bearing bolts to the frame or underbody of the
vehicle. It supports the center of the drive shaft where
the two shafts come together.
A sealed ball bearing allows the drive shaft to spin
freely. The outside of the ball bearing is held by a thick,
rubber, doughnut-shaped mount. The rubber mount
prevents vibration and noise from transferring into the
A bearing similar to the center support bearing is
often used with long drive lines, containing a single
drive shaft. This bearing is called a PILLOW BLOCK
BEARING. It is commonly used in drive lines that
power auxiliary equipment. Its purpose is to provide
support for the drive shaft and maintain alignment.
When used at or near the center of the shaft, it reduces
the whipping tendency of the shaft at high speed or
when under heavy loads. The construction of pillow
blocks varies. The simplest form is used on solid power
takeoff drive shafts, which is no more than a steel
sleeve with a bronze bushing.
DRIVE LINE MAINTENANCE
A drive line is subjected to very high loads and
rotating speeds. When a vehicle is cruising down the
road, the drive shaft and universal joints or constant
velocity joints may be spinning at full engine rpm.
They are also sending engine power to either the front
or rear axle assemblies. This makes drive line
maintenance very important.
The drive shafts must be perfectly straight and the
joints must be unworn to function properly. If any
component allows the drive shafts to wobble, severe
vibration, abnormal noises, or even major damage can
Figure 5-10.Center support bearing.