COMPETENCY BASED LEARNING MATERIAL
Sector:
AUTOMOTIVE
Qualification:
Automotive Servicing NC II
Unit of Competency:
Service Suspension System
Module Title:
SERVICING SUSPENSION SYSTEM
Technical Education and Skills Development Authority
TESDA Complex, East Service Road, South Superhighway, Taguig, Metro Manila
NATIONAL CERTIFICATE LEVEL 2
QUALIFICATION LEVEL
COMPETENCY-BASED LEARNING MATERIALS
No. Unit of Competency Module Title Code
1. Service Starting System • Servicing Starting System ALT723307
2. Service Charging System • Servicing Charging System ALT723308
3. Service Engine Mechanical • Servicing Cooling System ALT723309a
System • Servicing Lubricating System ALT723309b
• Servicing Gasoline Fuel System ALT723309c
• Servicing Air Induction System ALT723309d
• Servicing Diesel Fuel Injector ALT723309d
4. Service Clutch System • Servicing Clutch System ALT723310
5. Service Differential and Front Axle • Servicing Differential and Front ALT723311
Axle
6. Service Manual Steering System • Servicing Manual Steering ALT723312
System
7. Overhaul Manual Transmission • Pulling-out, Disassembling and ALT723313a
Checking Manual Transmission
• Assembling and Testing ALT723313b
Manual Transmission
8. Service Brake System • Identifying and Explaining ALT723314a
Hydraulic Brake System
Operations and Functions
• Servicing Brakes ALT723314b
• Overhauling Brake Systems ALT723314c
9. Service Suspension • Servicing Suspension ALT723315
System System
HOW TO USE THIS COMPETENCY BASED LEARNING MATERIAL
Welcome to the module “Servicing Suspension System”. This module contains training
materials and activities for you to complete.
The unit of competency "Service Suspension System" contains knowledge, skills and
attitudes required for an Automotive Servicing. It is one of the specialized modules at National
Certificate level (NC II).
You are required to go through a series of learning activities in order to complete each
learning outcome of the module. In each learning outcome are Information Sheets and
Resources Sheets (Reference Materials for further reading to help you better understand the
required activities). Follow these activities on your own and answer the self-check at the end of
each learning outcome. You may remove a blank answer sheet at the end of each module (or
get one from your facilitator/trainer) to write your answers for each self-check. If you have
questions, don’t hesitate to ask your facilitator for assistance.
Recognition of Prior Learning (RPL)
You may already have some or most of the knowledge and skills covered in this learner's
guide because you have:
• been working for some time
• already completed training in this area.
If you can demonstrate to your trainer that you are competent in a particular skill or skills,
talk to him/her about having them formally recognized so you don't have to do the same training
again. If you have a qualification or Certificate of Competency from previous trainings, show it to
your trainer. If the skills you acquired are still current and relevant to the unit/s of competency
they may become part of the evidence you can present for RPL. If you are not sure about the
currency of your skills, discuss this with your trainer.
At the end of this module is a Learner’s Diary. Use this diary to record important dates, jobs
undertaken and other workplace events that will assist you in providing further details to your
trainer or assessor. A Record of Achievement is also provided for your trainer to complete
once you complete the module.
This module was prepared to help you achieve the required competency in servicing
suspension system. This will be the source of information for you to acquire knowledge and
skills in this particular trade independently and at your own pace, with minimum supervision or
help from your instructor.
Talk to your trainer and agree on how you will both organize the Training of this unit.
Read through the module carefully. It is divided into sections, which cover all the skills,
and knowledge you need to successfully complete this module.
Work through all the information and complete the activities in each section. Read
information sheets and complete the self-check. Suggested references are included to
supplement the materials provided in this module.
Most probably your trainer will also be your supervisor or manager. He/she is there to
support you and show you the correct way to do things.
Your trainer will tell you about the important things you need to consider when you are
completing activities and it is important that you listen and take notes.
You will be given plenty of opportunity to ask questions and practice on the job. Make
sure you practice your new skills during regular work shifts. This way you will improve
both your speed and memory and also your confidence.
Talk to more experience workmates and ask for their guidance.
Use the self-check questions at the end of each section to test your own progress.
When you are ready, ask your trainer to watch you perform the activities outlined in this
module.
As you work through the activities, ask for written feedback on your progress. Your
trainer keeps feedback/ pre-assessment reports for this reason. When you have
successfully completed each element, ask your trainer to mark on the reports that you
are ready for assessment.
When you have completed this module (or several modules), and feel confident that you
have had sufficient practice, your trainer will arrange an appointment with registered
assessor to assess you. The results of your assessment will be recorded in your
competency Achievement Record.
Qualification : Automotive Servicing NC II
Unit of Competency : Service Suspension System
Module Title : Servicing Suspension System
Introduction :
This module covers the skills and knowledge in diagnosing suspension system failure,
dismounting/mounting suspension component parts, disassembling/assembling suspension
parts and inspecting/replacing suspension component parts.
It consists of two (2) Learning Outcomes that contains learning activities for both
knowledge and skills supported with information sheet, job/operation sheet and self-check.
Before attempting to perform the manual exercises, see to it that you have already read and
understood the information/operating sheet and answer correctly the self-check provided in
every Learning Activities.
Upon completion of this module, you have to undergo the assessment to be administered
by your instructor. A certificate of completion (COC) will be given to you as a proof that you met
the standard requirements for this module. The assessment could be made in different methods
as prescribed in the competency standards.
Learning Outcomes :
At the end of this module you will able to:
1. Diagnose suspension system failure
2. Dismount/mount suspension component parts.
3. Disassemble/assemble suspension parts
4. Inspect/replace suspension component parts.
Assessment Criteria :
1.1 Causes of failure are identified and repair works recommended.
2.1 Suspension components are dismounted/mounted.
2.2 Dismounted parts are tagged/marked.
2.3 Parts are dismounted without causing damage to vehicle components
3.1 Suspension parts are disassembled/assembled.
3.2 Suspension parts are disassembled/assembled without causing damage to other
vehicle components/system.
3.3 Disassembled parts are rinsed with cleaning solution
4.1 Suspension system components are checked for cracks, loose nuts, bolts or bushing,
and leaks.
4.2 Damaged suspension parts are identified.
4.3 Damaged parts are replaced
Prerequisite : Before you tackle this module you must complete first the module in Overhauling
Brake System.
Code No. Date: Developed Date: Revised Page #
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Qualification : Automotive Servicing NC II
Module Title : Servicing Suspension System
Learning Outcome #1 : Diagnose suspension system failure
Assessment Criteria :
1. Causes of failure are identified and repair works recommended.
Resources :
1. Simulated workplace
2. Suspension mock-up
3. CD, Tapes, Transparencies, Books
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Learning Outcome 1: Diagnose Suspension System Failure. SPECIAL INSTRUCTIONS
LEARNING ACTIVITIES
Read information sheets LO1-
1. Identifying, explaining, and differentiating types of • 1, LO1-2 and LO1-3 to identify,
suspension system. explain and differentiate types
a. Purpose of Suspension System of suspension system. Answer
b. Front Suspension Types the self-check.
c. Rear Suspension Types
2. Identifying main components and function of • Read Information sheets LO1-
suspension system. 4 and LO1-5 to identify the
a. Types of Springs components and function of
b. Types of Shock Absorbers suspension system.
3. Explaining and illustrating the principle of • Read information sheets LO1-
operation of suspension system. 6 and LO1-7 to explain and
a. Spring Operating Principles illustrate the principles of
b. Shock Absorber Operating Principles suspension system.
• Can you identify the causes of suspension system • Read information sheets LO1-
failure? 8, LO1-9 and LO1-10 to
determine the causes of
1. Identifying causes of suspension system failure. suspension system failure.
a. Visual Inspection (Suspension parts)
b. Bounce Test. • Perform Job Sheet LO1-1
c. Suspension Ride Height Check • Operation Sheet LO1-1
d. Ball Joint Checks • Operation Sheet LO1-2
e. Checking Kingpin Clearance • Perform Job Sheet LO1-2
f. Control Arm Bushing Checks • Perform Job Sheet LO1-3
g. Strut Rod Bushing Checks • Perform Job Sheet LO1-4
h. Strut Checks • Perform Job Sheet LO1-5
• Perform Job Sheet LO1-6
• After learning activity 1, proceed to the next activity • After finishing this learning
• You can now identify suspension failure knowing all activity, answer the self
these causes?
checks.
• The next activity will help you identify suspension • Have your instructor check
failure.
your work before going any
2. Identifying suspension system failure further.
a. Suspension System Diagnosis Chart • Perform Job Sheet LO1-7
b. Road Test Vehicle
• After finishing this learning activity, answer self check
no. LO2-2 and compare your answer with the answer
key provided.
• Have your instructor check your work before going
any further.
• After learning activity 2, take the next activity.
• Have you already performed lifting a vehicle?
• The next activity will enable you to lift a vehicle
properly.
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3. Lifting a vehicle • Read Info. Sheet no. LO2-1
a. Hydraulic Jacks • Read Job Sheet no. LO2-9
• After finishing this learning activity, answer self check
no. LO2-3 and compare your answer with the answer
key provided.
• Have your instructor check your work before going
any further.
• After learning activity 3, take the next activity.
• Can you give some safety practices involved in this
type of job?
• The next activity will give you safety practices to be
observed in this type of job.
4. Observing vehicle, workshop area, and equipment • Read Info. Sheet no. LO2-2
safety procedure.
a. Shop Safety Rules
• After finishing this learning activity, answer self check
no. LO2-4 and compare your answer with the answer
key provided.
• Have your instructor check your work before going
any further.
• After completing all the learning activities included in
this module, take the Assessment to be conducted by
your trainer.
• Read Info. Sheet no. LO2-3
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INFORMATION SHEET LO1-1
Purpose of Suspension System
The front suspension of a vehicle is designed so the steering knuckle and spindle can
pivot on the steering axis to allow steering of the vehicle. The spindle must also rise and fall,
relative to the body, to allow the springs and shock absorbers to reduce bump and road shock
from the vehicle’s ride. The suspension system allows the springs and shock absorbers to
absorb the energy of the bump, so passengers can have a smooth ride. While doing these two
jobs, the suspension system must not allow loose, uncontrolled movement of the tire and wheel
and must keep the alignment of the tire as correct as possible.
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SELF CHECK LO1-1a
IDENTIFICATION
A. IDENTIFICATION: Identify the parts of the front suspension.
A. _____________________________________________
B. _____________________________________________
C. _____________________________________________
D. _____________________________________________
E. _____________________________________________
B. Identify these ball joints.
A. ___________________________________________
B. ___________________________________________
C. ___________________________________________
D. ___________________________________________
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C. Identify the parts of this suspension.
A. _____________________________________________
B. _____________________________________________
C. _____________________________________________
D. _____________________________________________
E. _____________________________________________
D. Identify the parts of this strut suspension
A. _____________________________________________
B _____________________________________________
C. _____________________________________________
D. _____________________________________________
E. _____________________________________________
F. _____________________________________________
E. Identify the parts of this swing axe suspension
A. ______________________________
B. ______________________________
C. ______________________________
D. ______________________________
E. ______________________________
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ANSWER KEY LO1-1a
(SUSPENSION)
A. IDENTIFICATION
A. Upper control arm
B. Upper ball joint
C. Spring
D. Steering knuckle
E. Lower control arm
B. Ball joints
A. Follower
B. Tension load carrying
C. Compression load carrying
D. Follower
C. Strut suspension
A. Damper/upper mount
B. Spring
C. Strut/shock absorber
D. Steering knuckle
E. Lower control arm
D. Strut suspension
A. Upper mount
B. Bearing
C. Insulator
D. Spring
E. Strut
F. Jounce bumper
E. Swing Axle
A. Pivot bushing
B. Axle
C. Steering knuckle
D. Radius arm
E. Spring
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SELF CHECK LO1-1b
1. Identify the parts of this ____ rear suspension
A. _______________________________
B. _______________________________
C. _______________________________
D. _______________________________
E. _______________________________
F. _______________________________
G. _______________________________
H. _______________________________
2. Identify the parts of this _____ rear suspension
A. _______________________________
B. _______________________________
C. _______________________________
D. _______________________________
E. _______________________________
3. Identify the parts of this _____ rear suspension
A. ____________________________
B. ____________________________
C. ____________________________
D. ____________________________
E. ____________________________
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4. Identify the parts of this leaf spring assembly
A. __________________________________
B. __________________________________
C. __________________________________
D. __________________________________
E. __________________________________
F. __________________________________
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ANSWER KEY LO1-1b
1. Solid axle
a. axle
b. control arm
c. driveshaft
d. torque arm
e. stabilizer bar
f. shock absorber
g. Panhard rod
h. Spring
2. Solid axle
a. pivot bushing
b. cross beam
c. spring and insulator
d. shock absorber
e. trailing arm
3. Strut
a. Spring
b. Stabilizer bar
c. Shock absorber
d. Knuckle
d. Control arm
4. Leaf spring assembly
a. bushing
b. center bolt
c. shackle
d. bushing
e. main leaf
f. spring clip/U-bolt
Code No. Date: Developed Date: Revised Page #
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SELF CHECK LO1-1c
TRUE OR FALSE (Front Suspensions)
1. In an S-L A suspension, the short upper arm is parallel to the longer, lower arm.
2. The upper and lower ball joints are the steering axis in an S-LA suspension
3. The roll center is at the center of the car on a line between the center of the tire’s road
contact and the instant center.
4. Placing the upper and lower control arms at angles (viewed from the side) creates a
resistance to brake drive
5. On most S-L A cars the load carrying ball joint is on the lower control arm
Multiple Choice
1. When a car is steered, the steering knuckle rotates on the
a. Steering axis c. Instant center
b. Roll center d. any of these
2. As the wheel of an S-L A suspension goes over a bump, the
a. vertical position
b. tire camber angle changes
c. track width changes
d. both a and b
3. The spring is on the lower control arm, and the steering knuckle is arranged so the outer
end of the control arm is between the ball joint bosses of the steering knuckle. This
control arm will use _____ ball joint
a. compression loaded, load carrying c. follower
b. tension loaded, load carrying d. none of these
4. The coil spring is mounted off-center on some struts to
a. reduce vibrations c. try to center the loads on the strut
b. increase spring leverage d. all of these
5. The upper strut mount c. dampens road vibrations
a. allows the strut to rotate d. all of these
b. allows the bottom of the strut to move sideways
Code No. Date: Developed Date: Revised Page #
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ANSWER KEY LO1-1c
TRUE OR FALSE
1. FALSE
2. TRUE
3. TRUE
4. TRUE
5. TRUE
MULTIPLE CHOICE
1. A
2. D
3. A
4. C
5. D
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SELF CHECK LO1-1d
TRUE OR FALSE (Rear Suspensions)
1. During acceleration, excessive rear axle windup can cause wheel hop.
2. A Panhard rod and a track bar do the same.
3. A semi-trailing arm suspension allows vertical tire motion with zero camber change
4. With IRS, wheel hop during acceleration is prevented by the control arms.
5. A torque arm is used on some coil sprung rear axles to prevent axle windup and wheel
hop
MULTIPLE CHOICE
1. In many year suspensions (a) a Panhard rod is used to control the sideways position of
the rear tires, (b) a stabilizer bar is used to reduce vehicle lean on turns. Which is
correct?
a. A only c. both A and B
b. B only d. neither A nor B
2. In coil spring, solid axle suspension (a) the fore-aft position of the axle is controlled by
track rods, (b) upper and lower control arms are used to control windup. Which is
correct?
a. A only c. both A and B
b. B only d. neither A nor B
3. In a leaf spring rear suspension, the spring can be used to locate the (a) fore-aft position
of the wheels, (b) sideways position of the axle. Which is correct?
a. A only c. both A and B
b. B only d. neither A nor B
4. In rear suspensions, (a) the lower control arms are used to locate the fore-aft position of
the tires (b) a rigid axle housing can maintain correct rear wheel alignment. Which is
correct?
a. A only c. both A and B
b. B only d. neither A nor B
5. Which of the following is not found in an RWD IRS?
a. Struts c. Control arms
b. A solid axle housing d. trailing arms
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ANSWER KEY LO1-1d
TRUE OR FALSE
1. TRUE
2. TRUE
3. FALSE
4. FALSE
5. TRUE
MULTIPLE CHOICE
1. C
2. B
3. C
4. C
5. B
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INFORMATION SHEET LO1-2
Types of Front Suspension
There are essentially five types of front suspensions used on cars, pickup, and trucks:
Short Long Arm (SLA), multilinks, MacPherson strut, swing axle, and solid axle.
SHORT-LONG ARM SUSPENSION
Short-long arm or SLA is the typical RWD
car’s front suspension. It also called an
unequal arm suspension. It consists of two
control arms (a short upper arm, and a longer
lower arm), a steering knuckle with spindle,
and the necessary bushings and ball joints
(Fig. LO1-2a). The control arms are usually
triangular. A-arm shapes with two inner pivot
bushings mounted on the car’s frame or
reinforced body structure. These control arms
are also called A-arms or wishbones. Another
type of lower control arm uses a single inner
pivot bushing along with either a trailing or a
leading strut rod. A trailing strut rod is also
called a tension rod because it has the pivot
bushing at the front and the control arm end at
the rear. A leading strut rod is also called a
compression rod; it has the pivot bushing at
the rear.
Figure LO1-2a. Two views of an SLA Suspension
system
The strut rod prevents forward or rearward
movement of the free (outer) end of the control
arm. The outer ends of both control arms
connect to the steering knuckle, which
includes the spindle, through a ball joint.
¾ S-LA Springs and Ball Joint
The car’s weight is transferred to the front
wheels through a spring. On SLA
suspensions, this is usually a coil spring:
torsion bars, leaf springs, or air springs also
can be used. The spring is commonly mounted
between the car’s frame and the lower control
arm and fender well, which is reinforced to
accept this load (Figure LO1-2b).
Figure LO1-2b. Cars without frames, or unibody
cars, usually position the spring between the upper
control arm and reinforced fender well.
Code No. Date: Developed Date: Revised Page #
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Newer multilink, long-knuckle SLA designs
use a strut-mounted spring (Figure LO1-2c).
Figure LO1-2c. This multilink suspension uses a
spring mounted over the shock absorber, like a
strut. The lower end is attached to the lower
control arm through a bushing.
The ball joint attached to the control arm
with the spring is called the load-carrying ball
joint because it must be constructed to carry a
portion of the car’s weight. Since a substantial
amount of load is on this joint, the joint can be
constructed with running clearance. The
vehicle load holds the joint tightly together,
eliminating any free play (Figure LO1-2d).
Some load-carrying ball joints are arranged
with the control arm positioned above the boss
or mount on the steering knuckle, so the load
squeezes the ball joint together. These are
called compression-loaded ball joints.
Figure LO1-2d. A vehicle load travels from the
frame or body, through the spring, along the
control arm, through a ball joint, and on through
the steering knuckle, wheel bearings, wheel, and
tire, to the ground.
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Most cars position the control arm under
the steering knuckle mount, so the load tries to
pull the ball joint apart. These are called
tension-loaded ball joints (Figure LO1-2e).
Figure LO1-2e. Depending on whether the control
arm is above or below the steering knuckle boss,
the load-carrying ball joint will be of a compression
or tension design.
The other ball joint is called the follower, Figure LO1-2f. The follower ball joint uses a
friction-loaded, steering, or dampening ball preload spring to keep the joint tight so it will have
joint. The follower joint carries no vertical load;
its major job is to keep the tire and wheel in no play or clearance.
alignment. This joint is built with slight internal
preload to prevent any looseness or freeplay;
this preload is not great enough to cause
steering drag. The follower and load-carrying
ball joints form the steering axis, the pivot
points for steering the front wheels (Figure
LO1-2f).
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Some vehicles use a type of ball joint and
tie rod end called low friction. These joints use
a very smooth ball and a socket that is lined
with a very slick polymer plastic material.
These joints are normally permanently
lubricated, use an improved grease seal, and
have no grease fitting. Low friction joints are
most common on lighter vehicles.
Multilink Suspensions
Some SLA designs have evolved so the
steering knuckle has become taller, about to
the top of the tire, and the spring is strut
mounted over the shock absorber. This design
is also called double-wishbone, wishbone-
strut, long-knuckle, or long-spindle SLA
(Figure LO1-2g).
Figure LO1-2g. This double-wishbone suspension
uses a spring and damper unit much like a strut
suspension. The long curved knuckle and very
angled upper control arm allow its use in areas of
limited size.
Strut Suspension
A strut suspension, often called a
MacPherson strut, has no upper control arm or
upper ball joint. The steering knuckle connect
to a spring and shock absorber assembly,
which is the strut. The upper end of this
assembly connects to the car body through a
pivot damper unit. A lower control arm is used;
it serves the same purpose as the lower
control arm is used; it serves the same
purpose as the lower arm of an SLA
suspension (Fig. LO1-2h). Many strut systems
use a control arm with a single inner pivot,
along with a strut rod.
Figure LO1-2h. Most control arms use two inner
bushings so both wheelbase and track can be
maintained A) Some control arms have a single
inner bushing and use a strut rod to maintain
wheelbase.
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Some strut systems mount the stabilizer
bar so that the end of the stabilizer bar can
serve as the strut rod (Figure LO1-2i).
The strut is basically a coil-over shock, or a Figure LO1-2i. This strut suspension uses a control
shock absorber with a coil spring mounted arm with a single bushing and controls the track
around it. The strut becomes shorter when the position of the tire. The wheelbase position is
tire moves upward over a bump and longer if controlled by the end of the stabilizer bar, which
the tire drops into a hole.. An oversize shock also serves as a trailing strut.
piston rod is required to withstand sideways
bending forces; vertical loads on the tire and Figure LO1-2j. Many struts have the spring seats
wheel result in sideways loads on the strut. located off-center to reduce the side load on the
This side load also tends to put a bind on he strut piston rod and bushing. Vehicle load tends to
strut motion. Some manufacturers mount the bend the strut sideways, the spring loads help
spring seats at an angle or off center to try and
reduce strut rod bind (Fig. LO1-2j). offset this tendency.
As the tire and wheel move up and down,
the ball joint lower control arm travels in an arc
similar to that of an S-L A suspension. As this
occurs, the lower end of the strut must move
inward and outward relative to the car; this
movement changes the vertical position of the
strut and therefore the camber angle. The
strut’s angle change is allowed by the design
flexibility of the upper strut mount or pivot-
damper assembly. The damper is also called
an insulator (Fig. LO1-2k).
Figure LO1-2k. The strut must change length
during suspension travel. The outer end of the
control arm must travel in an arc, just like the lower
control arm on an S-L A suspension.
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¾ Modified Struts
Some cars use a modified strut, in which Figure LO1-2l. A modified strut uses a spring
the spring is mounted on the lower control arm mounted on the lower control arm like an S-L A
instead of the strut. This is also called a single suspension. The strut serves as the upper end of
control arm suspension (Fig. LO1-2l). In this
suspension, the strut is essentially the same the steering axis with the shock absorber.
as a standard strut without the sprig mounts;
the upper strut mounts or dampers and pivots
are the same. The lower control arm and ball
joint are essentially the same as the lower
control arm on an S-L A suspension, and the
lower ball joint is a load-carrying ball joint.
A torsion bar can also be sued with a strut.
On these cars, the lower control arm usually
becomes the lever arm for the torsion bar (Fig.
LO1-2m).
Figure LO1-2m. In a strut suspension, the vehicle
load passes from the body, through the upper strut
mount, down trough the spring to the steering
knuckle, and on through the wheel bearings,
wheel, and tire to the ground (A) In a modified
strut, the load travels trough the spring and lower
control arm, like an S-L A suspension (B).
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Solid Axle
As mentioned earlier, solid axles are not Figure LO1-2n. A solid axle with springs and
used on passenger cars because of their steering linkage.
harsher ride and inferior handling
characteristics on uneven roads. They are
commonly used on trucks, 4WDs, and
some pickups because of their minimum
number of wear points. A solid axle is
simply a strong, solid beam of steel
(usually I shaped) with a kingpin at each
end to connect to the steering knuckle.
This axle is called a monobeam by one
manufacturer (Fig. LO1-2n).
Swing Axles, Twin I-Beam Axles
Swing axles, also called twin I-beam axles
have been used by Ford Motor Company
on its pickups, 4WDs, and light trucks.
Twin I-beam axles combine some of the
sturdiness and simplicity of a solid axle
with some of the improved ride and
handling characteristics of an independent
suspension types (Fig. LO1-2o).
Miscellaneous Suspension Types
Other front suspension types have been Figure LO1-2o. A twin I-beam front suspension.
used on cars, but these are not in current This particular swing axle design uses two ball
use or commonly used by any major joints to connect the steering knuckle to the axle.
manufacturer. The last one of these used
to a large extent was the trailing arm
suspension. The steering knuckle support
is attached to one or pair of trailing arms.
During travel over bumps, the tire and
wheel swing upward at the ends of the
trailing arms. There is zero camber or track
change. This suspension has a limitation in
that vehicle lean causes an equal change
in camber. This results in poor front-tire
adhesion while cornering (Fig. LO1-2p).
Figure LO1-2p. A twin trailing arm suspension. The
steering knuckle is supported by the two trailing
arms. Torsion bars are enclosed in the two
traverse tubes to function as the front springs.
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SELF CHECK LO1-2a
1. Identify the parts of this _____________ shock absorber
A. ____________________
B. ____________________
C. ____________________
D. ____________________
E. ____________________
F. ____________________
G. ____________________
H. ____________________
I. ____________________
2. Identify the parts of this ________________ shock absorber
A. ____________________
B. ____________________
C. ____________________
D. ____________________
E. ____________________
F. ____________________
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ANSWER KEY LO1-2a
1. Single tube
a. pressure tube
b. oil chamber
c. gas pressure chamber
d. piston rod\
e. working piston and valve
f. dividing piston
2. Double-tube
a. upper bayonet mount
b. piston rod
c. bushing and seal
d. pressure tube
e. reservoir tube
f. travel stop
g. piston and valves
h. base valve
i. lower ring mount
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SELF CHECK LO1-2b
TRUE OR FALSE (Spring)
1. Jounce is a term referring to a suspension’s vertical motion.
2. Downward travel of the suspension is called rebound
3. A very strong spring bounces at a higher frequency than a weak spring
4. A spring normally compresses from its free length when it is installed
5. Because of the leverage of the control arm, the end of the spring used in an S-L A
suspension travels about twice as far as the wheel during bounce
MULTIPLE CHOICE
1. A composite leaf spring has a somewhat tapered shape to
a. allow proper mounting c. provide a variable rate
b. speed manufacturing d. all of these
2. With an air spring, (a) car height for a parked vehicle is maintained by the rubber membrane,
(b) The spring rate rises during jounce. Who is correct?
a. A only c. both A and B
b. B only d. neither A nor B
3. With col springs, (a) coil clash is a sign of a sagged spring (b) a nick in the paint can cause
spring breakage. Which is correct?
a. A only c. both A and B
b. B only d. neither A nor B
4. With torsion bars, (a) a problem with low ride height can be corrected by adjusting them (b)
the main way to change the load rate is adjusting the length of the lever arm. Which is
correct?
a. A only c. both A and B
b. B only d. neither A nor B
5. Stabilizer bars c. add roll resistance to the suspension
a. reduce body lean on turns d. all of these
b. will make a one wheel bump harsher
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ANSWER KEY LO1-2b
TRUE OR FALSE
1. FALSE
2. TRUE
3. FALSE
4. TRUE
5. TRUE
MULTIPLE CHOICE
1. B
2. B
3. C
4. A
5. D
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SELF CHECK LO1-2c
MULTIPLE CHOICE (Shock Absorbers)
1. High pressure gas charges are used in shocks to
a. increase the shock’s spring rate c. reduce the unsprung weight
b. prevent mushy operation d. all of these
2. Air in the working chamber of a shock will cause (a) overheating, (b) mushy operation.
Which is correct?
a. A only c. both A and B
b. B only d. neither A nor B
3. In a single-tube shock absorber, the (a) extension valves are in the working piston, (b)
compression valves are in the base valve. Which is correct?
a. A only c. both A and B
b. B only d. neither A nor B
4. Computer controlled shocks use
a. sensors to determine various phases of a car operation
b. an actuator to change shock valving
c. the computer to determine proper shock settings
d. all of these
5. The best way to locate a faulty shock is to
a. inspect them visually
b. use the bounce test
c. give the car a road test
d. all f these
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ANSWER KEY LO1-2c
MULTIPLE CHOICE
1. B
2. B
3. A
4. D
5. D
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INFORMATION SHEET LO1-3
REAR SUSPENSION TYPES
Rear suspensions are very similar to front suspensions in that they allow vertical tire
movement. However, in most cases, they do not allow steering, and in cases in which four-
wheel steering is used, the steering is very limited.
Cars, pickups, vans, and trucks have
traditionally used driven, solid rear axles that
are sometimes called live axles. This sturdy
assembly holds the tires and wheels in
alignment, transfers the vehicle load from the
springs to the tires and wheels, and provides
the gearing necessary to transfer the power
from the driveshaft to he tires and wheels.
A solid axle is subject to the same Figure LO1-3a. The rear axle of a RWD car tends
movements possible from a front axle; windup, to wind up or rotate in response to acceleration
side shake, yaw and tramp. In a live axle, the and braking torque
action of sending power to the tires and
wheels and causing them to turn in a forward
direction produces a reaction of the axle
housing trying to rotate it in the opposite
direction. If we could see it, a hard
acceleration of the car produces a turning
force at the axle that tries to lift the front tires
and wheels. A “wheelie” by a drag race is a
dramatic example of this (Fig. LO1-3a).
¾ Solid Axle, Leaf Spring Suspension
The solid axle, leaf spring suspension is Figure LO1-3b. A leaf spring rear suspension
the simplest form of rear suspension. At one consists of the springs and shock absorbers
time, it was also the most common. A pair of
leaf springs attaches to the frame through a
rubber bushing at the front and trough rubber
bushings and a shackle at the rear. The rear
axle housing bolts solidly to the center of the
spring with a set of U-bolts. The front portion
of the spring acts as a control arm, positioning
the rear axle housing and establishing the
wheelbase (Fig. LO1-3b).
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¾ Solid Axle, Coil Spring Suspension
Because a coil spring does not have the Figure LO1-3c.This rear suspension has a single
ability to locate an axle, coil spring solid axles upper control arm to prevent axle rotation. Side
require more parts. A coil spring rear end motion is controlled by the track bar, also called a
usually uses two lower suspension arms Panhard rod; the track bar connects to the axle at
(sometimes called links) to control the rear
axle end of the wheelbase. It also uses one or the left end.
more upper suspension arms to control axle
windup and side motion. When two upper
arms are used, they are usually skewed
diagonally (mounted at an angle) to control
side motion as well as windup. The lower arms
are usually in a trailing and parallel position to
allow bind-free. Some designs use only one
upper arm to control axle windup plus a
Panhard rod, also called a track bar, to control
side motion (Fig. LO1-3c). A Panhard rod
connects to the axle, runs across the car, and
connects to the frame of the car. A flexible
bushing is used at each end. Sometimes a
Watt’s link is used in place of a Panhard rod
with a torque arm (Fig. LO1-3d).
Figure LO1-3d. This suspension uses a torque arm
to prevent axle windup. The track rod prevents
side motion, the stabilizer shaft reduces lean on
corners, and the lower control arms control the
wheelbase.
Figure LO1-3e. In early Corvettes (A) a single
trailing arm controlled wheelbase, brake torque,
and poe angle; Camber angle was controlled by
the axle shaft and the lower strut.
Independent Rear Suspension
Independent rear suspension (IRS) on Figure LO1-3f. In newer Corvettes (B) a five link
RWD vehicles has been used only on cars of suspension uses two trailing arms to control
luxury or sporty nature. IRS is more expensive
to build and has more wear points than a solid wheelbase and braking torque, a tie rod to control
axle, but it provides better ride qualities and toe angle, and a spindle support rod and axle shaft
usually better camber and toe control of the
rear tires (Fig LO1-3e and f). to control camber angle.
Code No. Date: Developed Date: Revised Page #
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¾ IRS, Semitrailing Arm Suspension
In the IRS, semitrailing arm suspension design, each rear tire and wheel is mounted on a
single control arm, which is usually mounted to the frame through one or a pair of rubber
bushings (Fig. LO1-3g).
Figure LO1-3g. Semitrailing arms support the rear wheel bearings to control camber and toe angles, as
well as control the wheelbase. Note the angles of the front pivot bushings that make these semitrailing
arms.
¾ IRS, Trailing Suspension
Chevrolet Corvettes use a trailing arm IRS,
but additional control links have been added to
provide better tire angle control (Fig. LO1-3h).
Figure LO1-3h. In early Corvettes, (A) a single trailing am controlled wheelbase, brake torque, and toe
angle; camber angle was controlled by the axle shaft and lower strut. In newer Corvettes, (B) a five link
suspension uses two trailing arms to control wheelbase and braking torque, a tie rod to control toe
angle, and a spindle support rod and axle shaft to control camber angle.
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¾ IRS Strut Suspension
Strut suspension in an IRS closely resembles the strut suspension used on front wheels
RWD strut suspensions are called Chapsman struts (Fig. LO1-3i).
Figure LO1-3i. This strut suspension uses two lower suspension arms to control track and toe angle; the
strut rod controls wheelbase.
Miscellaneous RWD Axle and Suspension
Types
At least three other RWD suspension types
have been used on cars, but their use is very
limited at this time. They include swing axle
(Fig. LO1-3j), low pivot axle, and de Dion axle
(Fig. LO1-3k).
Figure LO1-3j. A trailing arm with swing axle rear
suspension. The axles that control camber connect
to universal joints at the differential assembly.
Torsion bars are used for rear springs.
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Figure LO1-3k. This wheel drive van uses a de
Dion style axle. The driveline module containing
the differential is attached to the vehicle
underbody.
FWD Rear Axles
FWD cars use rather simple rear axles All
that is necessary is to allow the tire and wheel
to move up and down, while staying in
alignment. The suspension designs can be a
variation of any of the types previously
discussed. Most manufacturers use variations
of three styles: the solid axle, trailing arm, and
strut.
¾ FWD, Rear Solid Axle Suspension
A solid axle beam, usually of stamped Figure LO1-3l. A trailing arm, solid axle rear
steel, connects the two tires and wheels. A suspension from FWD car. The axle controls track
pair of tailing arms are bolted rigidly or welded
onto the axle beam and connect to the frame and the camber and toe angles, the trailing arm
through rubber bushings. control wheelbase, and the track bar controls side
The axle and trailing arms are somewhat motion.
flexible, to allow for slight twists when the car
leans on corners. Side motion of the axle is
controlled by a Panhard rod (Fig. LO1-3l).
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¾ FWD, Rear Trailing Arm Suspension
Each rear tire and wheel is attached to a
trailing arm. The trailing arm is attached to the
frame through a pivot bushing at the front.
Most FWD, rear trailing arm designs connect
the two trailing arms to each other with a cross
beam. This cross beam strengthens the
trailing arms and tends to reduce body roll; it
has to twist during body lean. Without the
cross beam, the trailing arms would operate
completely independently. (Fig. LO1-3m).
Figure LO1-3m. A trailing arm rear suspension. A
lateral beam (not shown) connects the two trailing
arms
¾ FWD, Rear Strut Suspension
Nonpowered rear struts normally used a strut, control arm, and strut rod to control rear tire
and wheel movement. The spring can be mounted on the strut or between the car body and the
lower control arm to save mounting room. In some designs, the lower control arm is replaced by
a pair of lateral links (Fig. LO1-3n.).
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Figure LO1-3n. Several styles of rear strut
suspensions for RWD cars. Note the type and
location of the spring and the different styles of
lower control arms.
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SELF-CHECK LO1-3
Answer the following briefly.
1. Enumerate the types of rear suspension used on light duty vehicle.
2. Differentiate each types of rear suspension.
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ANSWER KEY LO1-3
1. Enumerate the types of rear suspension used on light duty vehicle.
a. Solid Axle Leaf Spring Suspension
b. Solid Axle, Coil Spring Suspension
c. IRS, Semi Trailing Arm Suspension
d. IRS, Trailing Arm Suspension
e. IRS, Strut Suspension
f. FWD, Rear Solid Axle Suspension
g. FWD, Rear Trailing Arm Suspension
h. FWD, Rear Strut Suspension
i. FWD, Rear Short-Long Arm Suspension
2. Differentiate each types of rear suspension.
a. Solid Axle Leaf Spring Suspension – is the simplest form of rear suspension. A pair of
leaf springs attaches to the frame through rubber bushings at the front and through
rubber bushings and a shackle at the rear. The rear axle housing bolts solidly to the
center of the spring with a set of U-bolts. The front portion of the springs acts as a control
arm, positioning the rear axle housing and establishing the wheelbase.
b. This rear suspension has a single upper control arm to prevent axle rotation. Side motion
is controlled by the track bar, also called Panhard rod; the track bar connects to the axle
at the left end.
c. Semitrailing arms support the rear wheel bearings to control camber and toe angles, as
well as control the wheelbase. The angles of the front pivot bushings that make these
semitrailing arms.
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INFORMATION SHEET LO1-4
TYPES OF SPRINGS
Types of Springs
1. Coil Spring – The coil spring is made of
length of round spring-steel rod wound
into a coil. Some coil springs are made
from a tapered rod. This gives the
spring a variable spring rate. As the
spring is compressed, its resistance to
further compression increases (Fig. 1-
4a).
Figure LO1-4a. Types of springs
2. Leaf spring – two types of leaf spring
are single leaf and multileaf springs.
These have several flexible steel plates
of graduated length, stacked and held
together by clips. In operation, the
spring bends to absorb road shocks.
The plates bend and slide on each
other to permit this action (Fig. LO1-4b).
Figure LO1-4b. Rear-suspension system using leaf
springs, showing how the spring attaches to the
frame and axle housing
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3. Torsion Bar – The torsion bar is a
straight rod of spring steel, rigidly
fastened at one end to the vehicle
frame or body. The other end attaches
to an upper or lower control arm (Fig.
LO1-4c)
Figure LO1-4c Front suspension system using
longitudinal torsion bars.
4. Air Spring – The air spring (Fig. LO1-
4d) is a rubber cylinder or air bag filled
with compressed air. A plastic piston on
the lower control arm moves up and
down with the lower control arm. This
causes the compressed air to provide
spring action. If the load in the vehicle
changes, a valve at the top of the air
bag opens to add or release air. An air
compressor connected to the valve
keeps the air springs inflated.
Figure LO1-4d. Air spring which is a rubber
cylinder or air bag filled with compressed air
Code No. Date: Developed Date: Revised Page #
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INFORMATION SHEET LO1-5
SHOCK ABSORBERS
Figure LO1-5a. Construction of a simple shock
absorber
Purpose of Shock Absorbers
A shock absorber (Fig. 1-5a) is a tubular Shock absorber mounted in a shock absorber and
hydraulic device placed near each wheel to strut assembly with the coil spring.
control or dampen spring oscillations. One end
of the shock absorber attaches to the vehicle
body or frame. The other end attaches to a
moving suspension part such as the axle
housing or a control arm. Movement of the
spring then causes the shock absorber to
lengthen and shorten.
The purpose of the hydraulic shock Figure LO1-5b. shows the shock absorber action in
absorber is to dampen spring oscillations. It a variable damping strut. During normal driving,
does not support the weight of the vehicle, nor
does it affect vehicle height. grooves in the strut tube allow fluid to pass around
the piston. When the wheel suddenly drops into a
Shock Absorber Operation pothole in the road, the tube extends more than
normal. Now the piston is above the grooves. The
It is basically an oil-filled cylinder or tube in fluid can pass only through the holes in the piston.
which a piston moves up and down (Fig. 1). This increases the resistance to piston movement
This forces the oil or hydraulic fluid in the and reduces the impact of the suspension against
cylinder to flow through small fluid passages or
orifices in the piston. The resulting fluid friction its stops.
limits spring bounce.
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Figure LO1-5c. Shock absorber action in a variable
damping strut.
Other Types of Shock Absorber (Fig. LO1-
5c)
1. Spring-Assisted shock Absorbers – This
type combine spring action with shock
absorber action. This helps maintain proper
vehicle height regardless of load.
2. Adjustable Shock Absorber – It has three
positions that can be selected to change
the firmness of the shock absorber action.
Turning the upper dust tube one way
produces a softer ride. Turning it the other
way produces a harder ride. In some cars,
the driver can change the shock absorber
setting by moving a switch on the
instrument panel.
3. Air Shock Absorber – Have a rubber boot Figure LO1-5c. Various types of shock absorbers.
surrounding the shock absorber. This
forms a sealed air chamber which is filled
with compressed air. The compressed air
increases the load-carrying capacity of the
vehicle while maintaining proper rear-end
height.
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ALT723315 41
Many vehicles have automatic level control
or electronic level control (Fig. LO1-5d). The
two rear air shock absorbers are connected by
air lines to an air compressor on the vehicle.
At least one of the shock absorbers includes a
height sensor. It signals the electronic control
module (ECM) when the load in the rear of the
vehicle has caused a change in vehicle height.
The ECM then switches on the air compressor
to add air to the shock absorber. Removing
the load causes the ECM to open the air valve.
This bleeds air from the system.
Some vehicles have electronically-adjusted
air shocks or air struts at all four wheels.
Figure LO1-5d. Electronic automatic-level-control
system. A height sensor in the shock absorber
switches the electric air compressor.
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INFORMATION SHEET LO1-6
SPRING OPERATING PRINCIPLE
The springs make the load carrying connection between the suspension members and the
frame. Springs have the ability to bend or twist and absorb energy when they are compressed
to shorter lengths. When a tire meets an obstruction, it is force upward, and the energy of this
upward motion is absorbed by the spring rather than transmitted to the frame and body of the
vehicle. The spring however only absorbs this energy for a brief period; as soon as possible, it
releases the energy by extending back to its original length. This extension either pushes the
tire back down on the road or lifts the car if he obstacle is still under the tire.
When the spring releases its stored energy, it does so with such quickness and
momentum that the end of the spring usually extends too far. The spring goes through a series
of oscillations, contractions, and extensions until all of the energy in the spring is used up or
released. The speed of these oscillations depends on the natural frequency of the spring and
suspension. A car with undampened springs (i.e., no springs) tends to bounce up and down in
time to these oscillations. In most cases, this bounce frequency is disturbing to the driver or
passengers. A stronger spring oscillates at a faster frequency than a softer one. Many
manufacturers purposely mismatch the spring frequency at the front and at the rear to obtain a
flatter, more acceptable ride.
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INFORMATION SHEET LO1-7
SHOCK ABSORBER OPERATING PRINCIPLE
Figure LO1-7a Shock absorber locations (arrowed)
Spring oscillations are normally dampened or reduced by shock absorbers. Shock
absorbers are very poorly named. They do not absorb shock; the springs do. The shock
absorbers stop excessive spring oscillations. The shock absorber absorbs some of the energy
that was put into the spring by the bump and it converts the energy into heat that is dissipated
into the air. A shock absorber is usually mounted inside or next to each of the four springs on a
car (Fig. LO1-7a).
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INFORMATION SHEET LO1-8
DIAGNOSIS CHART
Condition Possible Cause Action
Vibration Wheel balance Check balance
Tire or wheel runout Check runout
Excessive noise Wheel or axle bearings Check bearings
Brake rotor or drum balance Check balance
Improper tire wear Driveline balance Check balance
Damaged driveline or U-joints Inspect driveshaft
Rough ride Engine balance Check balance
Vehicle leans or in Rough tires Check tire pressure
too high or low Loose or broken shock mounts Check mounts
Pulls or drifts right Damaged or worn suspension mounting insulators Check insulators
or left Incorrect air pressure Check inflation
Excessive toe Check alignment
Excessive camber Check alignment
Damaged shocks Check shocks
Broken or sagged springs Check ride height
Unequal tire pressure Check pressure
Mismatched tires Check tire size and types
Brake drag Check for free turning
Steering gear or linkage worn or damaged Check steering
Vehicle leans sideways or lengthwise Check ride height
Tight or worn suspension parts Check ball joints or strut
mount
Pulls during braking Incorrect toe settings Check alignment
Incorrect toe caster Check alignment
Wanders or requires Excessive caber or camber spread Check alignment
constant steering Excessive caster spread Check alignment
correction Worn suspension bushings Check suspension
Torque steer Brake problems Check brakes
Insufficient caster Check alignment
Steering wheel off Improper toe Check alignment
center Improper adjusted steering gear Check adjustment
Hard steering Improperly adjusted steering gear Check adjustment
Incorrect tire pressure Check inflation
Excess steering play Loose or worn engine or cradle mounts Check mounting
Improper driveshaft angles
Improper tracking Mismatched tires Check tires
Incorrect alignment Check alignment
Steering system problem Center steering
Excessive caster Check alignment
Binding steering gear Check steering gear
Power steering problem Check power steering
Binding ball joint or linkage Check steering system
Worn steering linkage Check steering system
Improper steering gear adjustment Check adjustments
Worn rack-and-pinion mounts Check mount bushings
Rear axle damage Check axle and mounting
Misaligned rear axle Check alignment
Figure LO1-8a. Steering and Suspension System Diagnosis Chart
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ALT723315 45
TROUBLE TREE
Figure LO1-8b. This is a procedure to locate the cause of a lead or pull condition. We
begin at the top and work our way until the cause is located and remedied.
Code No. Date: Developed Date: Revised Page #
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