chap90 pps Automotive technology at University of Cambridge

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Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

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OBJECTIVES:
After studying Chapter 90, the reader should
be able to:

• Prepare for ASE Suspension and Steering (A4)
•
•
•

certification test content area “A” (Steering
System Diagnosis and Service).

Identify steering linkage components.
Describe how the movement of the steering
wheel causes the front wheels to turn.
Describe how to perform a dry park test to
determine the condition of steering system
components.
Continued

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

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OBJECTIVES:
After studying Chapter 90, the reader should
be able to:

•
•
•

Perform an under-the-vehicle inspection of
the steering system components.
List the service procedures for under-the
vehicle steering system service.
Explain how to replace steering linkage parts.

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

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KEY TERMS:
articulation test • ball socket assembly
center link • center take-off rack • cross-steer linkage
dry park test • front steer • grease fitting
opposite-phase steering
parallelogram linkage • pitman arm • RBS • rear steer
same-phase steering • steering dampener • steering stops
• SWPS
tie rods • zerk fitting
Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

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The proper operation of the steering system is critical
to the safe operation of any vehicle.

Always follow the service procedures specified by the
vehicle manufacturer.

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

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STEERING LINKAGE
The steering linkage relays steering forces from the steering gear 
to the front wheels.
Most conventional steering linkages use the parallelogram­type 
design. A parallelogram is a geometric box shape where opposite 
sides are parallel and equal distance.
A parallelogram­type linkage uses four tie rods, two inner and 
two outer (left and right), a center link (between the tie rods), and 

an idler arm on the passenger side and a pitman arm attached to 
the steering gear output shaft (pitman shaft). 
See Figure 90–1.
Continued
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Figure 90–1 Steering movement is transferred from the pitman arm that is splined to the sector
shaft (pitman shaft), through the center link and tie rods, to the steeting knuckle at each front
wheel. The idler arm supports the passenger side of the center link and keeps the steering
linkage level with the road. (Courtesy of Dana Corporation)

Continued
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As the steering wheel is rotated, the pitman arm is moved. The pitman arm 
attaches to a center link. At either end of the center link are inboard (inner) tie 
rods, adjusting sleeves, and outboard (outer) tie rods connected to the steering 
arm. The passenger side of all these parts is supported and held horizontal by an 
idler arm that is bolted to the frame. 

The center link may be known by several names, including:
Center link
Connecting link
Connecting rod

Relay rod

Intermediate rod
Drag link (usually a truck term only)

Other types of steering linkages often used on light trucks and vans 
include the cross­steer linkage. 
See Figure 90–2. 
Continued
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Figure 90–2 The most common type of steering is the parallelogram. The cross-steer and
Haltenberger linkage designs are used on some trucks and vans.

Continued

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NOTE: Many light trucks, vans, and some luxury cars use a steering 

dampener attached to the linkage. A steering dampener is similar to a 
shock absorber, and it absorbs and dampens sudden motions in the steering 
linkage. 

Figure 90–3 Typical steering dampener used on a Hummer H2.
Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

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Why is a Grease Fitting Sometimes Called a Zerk Fitting?
In 1922 the zerk fitting was developed by Oscar U. Zerk, an employee of the
Alemite Corporation, a manufacturer of pressure lubrication equipment. A
zerk or grease fitting is also known as an Alemite fitting.

It is important that all of these joints be lubricated with chassis 
grease through a grease fitting, also called a zerk fitting, at least 
every six months or per the vehicle manufacturer’s specifications.
Some vehicles come equipped with sealed joints and do not require 
periodic servicing. Some vehicles come from the factory with 
plugs that need to be removed and replaced with grease fittings and 
then lubricated.
Continued
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Tie Rod Ends  Tie rod ends connect the steering linkage to the 
steering knuckles and to other steering linkage components.
Conventional tie rod ends use a hardened steel ball stud
assembled into a hardened steel and thermoplastic bearing.
An internal preload spring limits the ball stud endplay
and helps compensate for ball­and­socket wear.
See Figure 90–4.
Ford Motor Company used tie rod ends that included a rubber­
bonded steel ball stud. Because there is no  sliding friction inside 
the tie rod end, no lubrication was needed. This type of tie rod end 
is called RBS (rubber­bonded socket).
See Figure 90–5.

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

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Figure 90–4 (a) A dual bearing design with a preload spring. The use of two bearing surfaces
allows for one surfaces for rotation (for steering) and another surface for pivoting (to allow for
suspension up-and-down movement). (b) The nylon wedge bearing type allows for extended lube
intervals. Wear is automatically compensated for by the tapered design and spring-loaded
bearing.

(a)

(b)

Continued
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Figure 90–5 (a) A rubber-bonded socket is constructed of a rubber casing surrounding the ball
stud, which is then inserted into the socket of the tie rod end. The hole in the socket allows air
to escape as the ball stud is installed and there is not a place for a grease fitting. (b) The socket
is crimped over the ball so that part of the socket lip retains the stud.

(a)

(b)

Continued

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RACK-AND-PINION INNER TIE ROD ENDS
Inner tie rod end assemblies used on rack­and­pinion steering units 
require special consideration and often special tools. The inner tie 
rod end is also called a ball socket assembly.
Figure 90–6 Rack-and-pinion steering
systems use a ball-and-socket-type
inner tie rod end.

The inner tie rod assemblies 
are attached to the end of 
the steering rack by one of 

several methods. 

Continued
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Figure 90–7 A variety of methods are used to
secure the inner tie rod end socket assembly
to the end of the rack.

Riveted or Pinned  Found on 
Ford vehicles. Some roll pins 
require a special puller, or the 
pin can be drilled out. 

Many use an aluminum rivet. 
A special, very deep socket or 
a large open­end wrench can be 
used to shear the aluminum 
rivet by unscrewing the socket 
assembly from the end of the 
rack while the rack­and­pinion 
unit is still in the vehicle. 

Continued
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Staked  Common on Saginaw­style rack­and­ pinion steering 

units found on GM vehicles. The flange around the outer tie rod 
must be restaked to the flat on the end of the rack.
Figure 90–8 Exploded view of a center-take-off-style
rack-and-pinion steering gear assembly.

Center Take­Off Racks 
For the center take­off 
racks, use bolts to secure 
the inner tie rods to the 
rack, as shown here.

Continued
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Front Steer versus Rear Steer Front steer  also called forward 
steer, is used to describe a vehicle that has steering gear in front
of the front wheel centerline. Having the steering gear located
in this position improves handling and directional stability, 
especially when the vehicle is heavily loaded.
Front­steer vehicles usually produce an understeer effect that 
makes the vehicle feel very stable while cornering. Most front­
wheel­drive vehicles are rear steering, with the rack­and­pinion 
steering unit attached to the bulkhead or subframe behind the 
engine.
See Figure 90–9.

Continued
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Figure 90–9 In a rear-steer vehicle, the steering linkage is behind the centerline of the front
wheels, whereas the linkage is in front on a front-steer vehicle.

If the steering gear linkage is located behind the wheels, it is called 
rear steer and the cornering forces are imposed on the steering in 
the direction of the turn. This is an oversteer effect. It tends to make 
the steering easier and makes the vehicle feel less stable.
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FOUR-WHEEL STEERING

Some vehicles were equipped with a system that steers all four 
wheels. Two terms are commonly used when discussing four­wheel 
steering:

1. Same­phase steering means the front and rear wheels are 
steered in the same direction. This improves steering response, 
especially during rapid­lane­change­type maneuvers.
2. Opposite­phase steering called negative­phase mode, the 
front wheels and rear wheels are steered in the opposite 
direction. Opposite­phase steering will quickly change the 
vehicle’s  direction, but may cause a feeling of oversteering.
See Figure 90–10. 
Continued
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Figure 90–10 Opposite-phase four-wheel steer is usually used only at low vehicle speed to help
in parking maneuvers. Sample-phase steering helps at higher speeds and may not be
noticeable by the average driver.

Opposite­phase 
steering is best at low 
speeds; same­phase 
steering is best for 
higher­speed handling 
and lane­change 
maneuvers.

Continued
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Quadrasteer  A four­wheel steering system that dramatically 
enhances low­speed maneuverability Quadrasteer™ gives high­
speed stability, and towing capability. 
Figure 90–11 Being equipped with fourwheel steer allows a truck to make shorter
turns than would otherwise be possible.

The system is an electrically 
powered rear wheel steering 
system comprised of the 
following components:
A steerable, solid rear axle
A heavy­duty wiring harness 
and fuse
A programmable control 
module
Continued
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A power relay in the control module
A rack­and­pinion­style steering actuator mounted on the rear 
differential cover
An electric motor assembly on top of the rear steering actuator
Three Hall­effect switches in the motor assembly
A shorting relay in the motor assembly
A rear wheel position sensor located under a cover on the 
bottom of the actuator, below the motor assembly
A steering wheel position sensor located at the base of the 
steering column
A mode select switch on the dash

Continued
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Figure 90–12 The Quadrasteer system includes many components that all work together.

Overall view of the components 
of the Quadrasteer system.
Continued
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The rear wheel steering control module has the following inputs:
Battery voltage
Switched battery voltage
Class 2 serial data

Figure 90–13
Rear steer select switch schematic.

Steering wheel position sensor 
analog signal, via class 2 message 
from body control module (BCM)
Steering wheel position sensor 
phase A
Steering wheel position sensor 
phase B
Steering wheel position sensor 
marker pulse
Rear wheel position sensor 
position 1
Rear wheel position sensor 
position 2

Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition
By James D. Halderman

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