252 Auto Suspension and Steering
Introduction
This chapter covers the components related to vehicle
drivelines and wheels. While some of these components
are not directly related to the suspension and steering
systems, they can cause vibration, noise, and other
problems. These problems are often blamed on the
suspension and steering components. Therefore, the sus-
pension and steering technician must be familiar with the
design and operation of drivelines and wheels so the real
cause of problems can be determined.
Studying this chapter will illustrate how drivelines and
wheel components fit into the overall vehicle design, and
how they can affect vehicle operation. This chapter
will also discuss the design and materials used in the
construction of these parts.
Driveline Components
Driveline components consist of the drive axles and
shafts, flexible joints, and related parts. Drive axles can be
roughly divided into solid and independent types. As a
general rule, solid axles are used on rear-wheel drive
vehicles and independent axles are used on front-wheel
drive vehicles. There are exceptions to this rule, especially
on sport-utility vehicles and sports cars. The application
and construction of both solid and independent drive axles
is discussed in the following section.
Several types of flexible joints are used on modern
vehicles. The type of flexible joints used depends on the
type of axle. Design and use of flexible joints is also
discussed below.
Independent Drive Axles
Independent drive axles are usually called CV axles
because they use a type of flexible joint called a CV joint.
All front-wheel drive vehicles, as well as a few rear-wheel
drive cars, use CV axles. CV axles are solid steel shafts that
connect the transaxle output shafts to the wheels. A few CV
axles are constructed of hollow tubes to reduce weight and
rotating mass. There are always two CV axles on a front-
wheel drive vehicle. Figure 12-1 shows a typical CV axle
assembly. Note that there are four CV joints, two on each
axle.
On a few vehicles, a transfer shaft, or intermediate
shaft, is used between the transaxle and the CV shaft on
one side of the vehicle, Figure 12-2. Use of a transfer shaft
allows a support bearing to be placed midway between the
transaxle and the wheel. This reduces vibration and strain
on the CV axle components. Transfer shafts are used on
large cars and on cars with manual transaxles when there
is a large distance between the transaxle case and the
wheels.
A few high-performance or sports cars use an
independent rear axle, with exposed drive shafts
containing CV joints. The construction of these shafts is the
same as those used on a front-wheel drive vehicle. Some
older independent rear axle shafts use U-joints instead of
CV joints.
Solid Drive Axles
On most rear-wheel drive cars and trucks, the drive
axles are solid steel shafts. The shafts extend from the
differential assembly gears to the wheel rims. Inside the
axle housing, external splines on the axle shafts mate with
internal splines on the differential gears. The shafts are
enclosed in the rear axle housing and are supported by
bearings.
Solid axle shafts are held in place by one of two
methods. One design locks the shaft in place with an
external retainer behind the brakes, while the other secures
the shaft with a C-lock located inside of the differential
assembly. Each design is shown in Figure 12-3.
Seals keep lubricant from leaking from the axle
housing. Remember from Chapter 7 that the rear axle may
be called a Hotchkiss axle or a Salisbury axle, depending
on the type of rear springs used.
A few four-wheel drive vehicles have a solid front axle
with solid shafts. To allow the vehicle to turn, the ends of
the shafts are attached to the wheel through flexible joints,
Figure 12-4.
CV joints
CV axle
assemblies
Intermediate
shaft
CV axle assembly
Support bearing
CV
assembly
Figure 12-2. This front-wheel drive vehicle uses an
intermediate shaft assembly. Study the layout.
Figure 12-1. Typical front-wheel drive axle assembly.