Suspension service 489 Maintenance 490 Dismantling and reassembling procedures 490 Ball joint front suspension 491 Strut (McPherson) suspensions 492 Rigid rear axle with coil springs 494 Independent rear suspension (RWD vehicles) 495 Rigid rear axle with leaf springs 496 Dismantling and reassembling struts 498 Servicing components 499 Servicing hubs and bearings 502 Hubs with tapered roller bearings 502 Hubs with unitised bearings 504 Other bearing arrangements 506 Checking suspension parts 507 Servicing shock absorbers 509 Technical terms 510 Review questions 510
Trang 1Suspension service
Chapter 28
Maintenance
Dismantling and reassembling procedures
Ball joint front suspension
Strut (McPherson) suspensions
Rigid rear axle with coil springs
Independent rear suspension (RWD vehicles)
Rigid rear axle with leaf springs
Dismantling and reassembling struts
Servicing components
Servicing hubs and bearings
Hubs with tapered roller bearings
Hubs with unitised bearings
Other bearing arrangements
Checking suspension parts Servicing shock absorbers Technical terms
Review questions
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Suspension service can include lubrication of ball
joints, lubrication of wheel bearings, removing and
replacing damaged or worn suspension parts, checks
and adjustments for alignment, and removing and
replacing shock absorbers.
This chapter deals with methods of removing and
installing suspension components and general
suspension servicing Wheel alignment is covered in a
later chapter.
Maintenance
Suspension maintenance consists of checks and, in
some cases, lubrication Arms and linkages are
checked for looseness, rubber bushes for wear, ball
joints for wear, and rubber boots for deterioration.
Suspension plays an important part in steering, and so
the vehicle’s suspension is checked during a wheel
alignment.
Ball joints are packed with grease during
manu-facture and usually need no further lubrication.
However, they can be lubricated by partially filling the
boot with grease.
Some ball joints in the front suspension of light
commercial vehicles can be lubricated with a grease
gun These have grease nipples, or plugs that can be
removed so that grease nipples can be fitted.
The bearings in some wheel hubs have to be
dismantled for servicing, but others normally do not
need servicing.
Dismantling and
reassembling procedures
The dismantling procedure will vary for different types
of suspensions, but supporting the vehicle correctly
and relieving the force of the spring are the first steps.
While this is necessary for dismantling, it is also
essential for safety With some suspensions, the spring
is removed separately; with others, the spring is
removed with other components.
Reassembling is, in general, the reverse of
dis-mantling, with parts being reinstalled in the reverse
sequence For this reason, the text that follows relates
mainly to dismantling A number of different types of
suspensions will be used as examples of the types of
operations that are carried out on suspension systems.
■ Because of the many variations in suspension
design, reference will have to be made to workshop
manuals for actual procedures.
Supporting the vehicle
With the wheels on the ground, the springs and other suspension components are under load Before the suspension can be dismantled, the load must be relieved by having the vehicle correctly supported The vehicle is raised with a floor jack and stands placed at the correct jacking points under the sill panel
or subframe When the jack is lowered, the stands will support the body and let the wheels hang free This takes the load off the parts of the suspension that are to
be dismantled (Figure 28.1).
figure 28.1 The vehicle must be supported correctly
when working on the suspension DAIHATSU
With the vehicle correctly supported, the spring will be extended, and the suspension will be sitting on its rebound bump stop or hanging on its shock absorber This will depend on the type of suspension.
A jack can then be used to raise or lower the ion as required.
suspens-Suspension work can be done with the vehicle on the floor with the aid of jacks and stands, but it can also be done with the vehicle on a hoist, provided it is suitably supported.
■ With any design of suspension, it is dangerous to try to remove any suspension component unless the vehicle is correctly supported.
Preliminary work
Certain preliminary work is common to most pensions This is work that has to be done before the actual suspension parts can be dismantled It includes the following:
sus-1 Removing the wheel to gain access to the ion components.
suspens-489-510_May_chap 28 12/9/06 10:48 AM Page 490
Trang 33 Disconnecting the stabiliser bar from the control
arms.
4 Removing brake components from their mountings.
5 Disconnecting steering connections.
■ The actual parts that have to be removed will
depend on the particular design of suspension.
Finalising after reassembling
After reassembling a suspension, the bolts securing
arms and linkages are tightened to the specified torque.
Before being finally tightened, the vehicle should be
resting on its wheels and free of jacks and stands.
Bounce the vehicle up and down a number of times to
allow rubber bushes to settle and then carry out the
final tightening.
The position of any parts that have a bearing on
wheel alignment or adjustment should be marked
before dismantling to assist with reassembly For
example, a steering knuckle and its mounting on the
strut might be marked so that they can be reassembled
in exactly the same position (Figure 28.2).
After reassembling and before finally tightening the
mounting bolts, the marks can be accurately aligned so
that the wheel camber will not be affected.
Ball joint front suspension
With ball joint suspension of the design shown in Figure 28.3, the coil spring sits on the lower control arm (9), and its upper end has a mounting on the front crossmember (1) To remove the spring, the outer end
of the control arm has to be lowered so that the spring will extend fully.
The shock absorber is mounted inside the coil and will have to be removed first The outer end of the
figure 28.2 A strut and knuckle are marked before
dis-mantling
mark position
strut
bolts
bracket
knuckle
figure 28.3 Coil suspension with upper and lower control arms
1 crossmember, 2 control arm pivot, 3 bump stop, 4 upper control arm, 5 upper ball joint, 6 knuckle, 7 spindle,
8 lower ball joint, 9 lower control arm, 10 bump stop, 11 spring, 12 spring seat, 13 lower control-arm pivot
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control arm is freed by removing the stud of the lower
ball joint (8) from the steering knuckle (6) The end of
the control can then be lowered with a jack to free the
spring With the spring no longer in compression, it
can be safely removed.
During dismantling, the vehicle is supported under
the front crossmember or subframe, and a jack is used
to support the lower control arm and to lower it to
extend the spring.
Strut (McPherson) suspensions
Struts are used for front suspensions and also for rear
suspensions They are used in conjunction with
rear-wheel drive, with front-rear-wheel drive and with all-rear-wheel
drive The strut and spring arrangement are basically
the same wherever they are used, but there are
different things to be considered when a strut is to be
removed Some of these are:
1 Arms and linkages The arms and linkages are not
the same for all suspensions and this can vary the
dismantling procedure.
2 Steering parts With front-wheel drive, there are
steering parts and also the drive shaft from the
transaxle to consider.
3 Steering knuckle With front struts, the steering
knuckle is attached to the strut This is usually
bolted, but it can be part of the strut (The steering
knuckles are different for driving and non-driving
wheels.)
4 Wheel hubs With both front and rear struts, the
arrangement of the wheel hub and/or axle spindle
for driving wheels is different from non-driving
wheels.
5 Springs In almost all cases, the strut and spring are
removed together, with the spring held compressed
with a special tool.
6 Mountings Similar mountings are used at the top of
all struts, but the lower mounting can be different.
Front strut (rear-wheel-drive vehicle)
The components of a strut-type front suspension are
shown in Figure 28.4 The suspension is for a
rear-wheel-drive vehicle The following parts can be
identified:
1 Strut The strut (4) contains the shock absorber
components It has a seat for the lower end of the
spring.
2 Spring The coil spring (3) is mounted over the strut and sits on the spring seat It is held in a compres- sed state between the spring seat and the upper mounting (2).
3 Upper mounting When installed in the vehicle, the top of the strut (2) is bolted to the reinforced mounting of the spring tower (1).
4 Lower mounting The lower end of the strut is bolted to the ball joint (10) on the lower control arm.
5 Lower control arm The lower control arm (11) carries the ball joint (10) and is connected to the front crossmember (16) by bolts and rubber bushes.
6 Tension rod The tension rod (13) is connected between the front crossmember and the lower control arm There are rubber bushes (15) at each end of the rod The threaded rod allows limited adjustment.
7 Stabiliser bar A link (9) connects the end of the stabiliser bar (14) to the lower control arm (11) The top of the link fits into the eye in the stabiliser bar and the lower end of the link fits into a hole in the lower control arm Rubber bushes are fitted at the top and bottom of the link.
8 Wheel hub assembly The strut has a fixed spindle
on which the wheel hub (6) and bearings are mounted Other parts are the brake disc, the brake caliper (7) and the dust shield (5).
■ Suspension parts can be removed and replaced without removing the strut from its upper mounting, provided the vehicle and components are correctly supported If the spring or strut require service, then they are removed as an assembly.
Front strut (front-wheel-drive vehicle)
Figure 28.5 shows the lower end of a strut, the steering knuckle and the associated components for a front- wheel-drive vehicle The strut itself is similar to the one in the previous illustration, but it has a knuckle that is bolted to the strut that is quite different.
The knuckle is designed with a boss with a large hole to carry the hub and bearing for the front wheel The bearing is a unitised bearing with a double row of balls It is not adjustable The bearing is retained in the knuckle by a snap ring.
The knuckle is connected to the control arm by the ball joint, which allows the knuckle and strut to be turned for steering.
489-510_May_chap 28 12/9/06 10:48 AM Page 492
Trang 5A boss on the hub fits into the bearing The hub has
internal splines, which accommodate the splines on
the end of the drive shaft The hub is retained in the
bearing and the shaft is retained in the hub by a nut and
washer on the end of the drive shaft.
The dust shield and the brake caliper are mounted
on the steering knuckle The brake disc is bolted to the
wheel hub.
Rear strut (front-wheel-drive vehicle)
When dismantling a rear strut suspension for a
front-wheel-drive vehicle, a floor jack is used to raise the
vehicle Stands are then placed under the jacking
points at the rear of the sill panel to support the body
of the vehicle, as shown in Figure 28.6.
The lower mountings of the suspension are
accessible with the wheel removed, and the upper strut
mounting is accessible from the interior of the vehicle.
Dismantling points
The general dismantling sequence for this type of suspension is to disconnect the lower end of the strut, then the upper end so that the strut complete with the spring can be removed The trailing arm and lateral arms can then be dismantled as required.
In some cases, the strut is too long to be easily removed and it has to be compressed before this can be done The jack is placed under the lower control arm and the strut and spring are compressed The com- pressing tool is then fitted to hold the spring in this condition The compressed strut is short enough to enable it to be removed.
■ Again, when handling and compressing springs, safety precautions should be observed.
figure 28.4 Strut-type suspension for the front wheel of a rear-wheel-drive vehicle
1 spring tower, 2 strut mounting, 3 spring, 4 strut, 5 dust shield, 6 wheel hub, 7 brake caliper, 8 stabiliser link
bushes and washers, 9 stabiliser link, 10 ball joint, 11 lower control arm, 12 stabiliser link bushes and washers, 13 tension rod,
14 stabiliser bar, 15 tension rod bush, 16 front crossmember HOLDEN LTD
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Rigid rear axle with coil springs
There are several different arrangements of rigid rear
axles with coil springs One arrangement is illustrated
in Figure 28.7 One side of the suspension is shown
assembled and the other dismantled The suspension
has upper and lower control arms (The lower control
arm is a trailing arm.) It has a Panhard (lateral) rod.
Removal of parts
1 A floor jack is used to raised the rear of the vehicle
and stands are placed under the rear jacking points.
2 The jack remains in place to support the rear-axle housing.
3 The Panhard rod is disconnected or removed.
4 The lower ends of the shock absorbers are connected from their mountings.
dis-5 The jack and axle housing are lowered This allows the coil springs to extend so that they can be removed.
6 With the springs removed, there is no loading on the remaining suspension parts and further dismantling can be carried out.
7 The lower control arms are disconnected from the axle housing, or removed.
8 After the control arms are disconnected, the axle housing is free as far as the suspension is concerned.
■ If the axle housing is to be completely removed, the propeller shaft will have to be disconnected at the pinion flange.
Dismantling points illustrated
Some of the dismantling points for a suspension with
a rigid axle and coil springs are illustrated in Figure 28.8.
figure 28.5 Components of a hub assembly for a strut suspension (front-wheel-drive vehicle)
1 brake caliper, 2 drive shaft, 3 strut, 4 mounting bracket, 5 steering ball, 6 knuckle, 7 dust shield, 8 brake disc,
9 wheel hub, 10 washer, 11 drive shaft nut, 12 snap ring, 13 bearing, 14 ball joint, 15 control arm, 16 clamp bolt for ball joint
MAZDA
figure 28.6 Position of jack and stands for dismantling a
rear suspension with struts DAIHATSU 489-510_May_chap 28 12/9/06 10:48 AM Page 494
Trang 7Independent rear suspension
(RWD vehicles)
There are two general designs of independent rear
suspension (IRS) for rear-wheel-drive vehicles These
are strut-type suspension and trailing-arm suspension.
Both of these have swing axles, or open drive shafts,
between the differential assembly and the rear
(driving) wheels.
IRS with struts
Figure 28.9 shows a rear-axle crossmember assembly
with a strut-type suspension system The differential
assembly is bolted to the centre of the crossmember and
the crossmember is bolted to the subframe of the vehicle.
The suspension has upper and lower control arms
that are mounted to the crossmember The coil springs
fit over the struts The struts have an upper mounting
to the body and a lower mounting to the lower control arm (Also see Figure 28.13.)
The upper strut mounting is accessible from inside the vehicle and the lower from the rear of the vehicle With the vehicle supported on stands, the suspension can be lowered enough to remove the strut complete with the spring and upper mounting.
IRS with coil springs
Figure 27.20 (in the previous chapter) illustrates an independent suspension with coil springs and trailing arms The dismantling procedure is similar to that previously outlined for a rigid axle with coil springs, except that the drive shaft has to be considered Also, the arrangement of the wheel hub, if that part of the assembly is to be dismantled.
The drive shaft and the wheel hub are connected by flanges that are bolted together To separate the drive
figure 28.7 Rear suspension with a rigid-axle assembly and coil springs HOLDEN LTD
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shaft, the flange bolts are removed (Figure 28.10) The
drive shaft can then be moved away.
The drive shaft should be tied up to the
cross-member and not allowed to drop This is done to
prevent damage to the constant-velocity joint boot.
Rigid rear axle with leaf springs
The components of a leaf spring suspension are shown
in Figure 28.11 This type of suspension is used with
some station wagons and light commercial vehicles.
To remove the spring, the axle housing has to be
lifted away from the spring The spring can then be
disconnected, first at the rear end and then at the front.
The procedure is as follows:
1 Raise the vehicle with a jack under the centre of the
rear-axle housing, and place stands under the
subframe to support the rear of the vehicle.
2 Remove the wheel to make the spring more accessible.
3 Disconnect the shock absorber at its lower ing, or at both mountings if it is to be removed.
mount-4 Lower the jack so that the springs hang.
5 Remove the nuts from the U-bolts and remove the spring plate and insulator from under the spring.
6 Remove the U-bolts and raise the jack until it lifts the rear axle from the spring The jack now supports the rear-axle housing.
7 Disconnect the rear shackle and lower the end of the spring to the floor.
8 Remove the bolt from the spring hanger at the front
of the spring and remove the spring.
figure 28.8 Service points on removing a rear axle and coil-spring suspension MITSUBISHI
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Trang 9Dismantling leaf springs
Leaf springs are held together by a centre bolt and spring clips To separate the leaves, the spring clips are opened up and the centre bolt is removed The centre bolt is under tension and the spring must be clamped in
a vice to hold the leaves together This must be done to relieve the load on the centre bolt before it is removed The centre bolt is a special bolt with a round head that, apart from holding the spring together, is used to locate the rear-axle housing in its correct position The round head of the bolt fits into a hole in the centre of the spring seat provided for this purpose.
While this bolt is called a centre bolt, it is not necessarily in the centre of the spring, as one end of the spring is usually longer than the other.
Generally, the front of the spring can be identified
by the size of the eye or type of spring mounting Where there is no obvious difference between the front and rear, make sure that the spring is not installed back-to-front.
■ Should a spring be incorrectly installed, the rear axle would be out of alignment and this would cause steering problems and tyre wear.
figure 28.9 Rear-axle crossmember and suspension assembly for a rear-wheel-drive vehicle with independent rear
suspension FORD
inner joints
upper control arm
upper mounting
coil spring
brake backing plate
hub handbrake shoe
lower control arm
mounting point inner joint
differential assembly mountings
mounting point
figure 28.10 Disconnecting the drive shaft of an IRS at the
wheel hub HOLDEN LTD
drive shaft
ratchet handle
CV joint
flange bolts
shock absorber
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Dismantling and
reassembling struts
Figure 28.12 shows a dismantled strut This is a front
strut, but rear struts are the same, except for the upper
mounting With the spring compressed, the strut can be
dismantled as shown The shaft nut at the top of the
strut retains the parts in place Once that is removed,
the upper mounting can be removed, followed by the
spring seat, the upper insulator, the coil spring, the
bump stop, and the dust cover.
The shock absorber part of the strut cannot be
dismantled and, if faulty, would have to be replaced
with either a new or a reconditioned unit.
Rear suspension strut
The mountings for a rear-suspension spring and strut
are shown in Figure 28.13 This particular strut has its
lower end mounted to the lower control arm wise, it is similar to other struts.
Other-1 Figure 28.13(a) shows the dismantled parts of the strut.
2 Figure 28.13(b) shows how the upper end of the coil is located in the insulator, which is shaped to fit.
3 Figure 28.13(c) shows the lower end of the spring and how it fits on to the spring seat on the strut.
4 Figure 28.13(d) shows how the strut is mounted to
a reinforced part of the body above the rear wheel arch The nuts securing the strut are accessible from inside the body.
figure 28.11 Components of a rear suspension with a rigid rear axle and leaf springs FORD
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Trang 11Servicing components
The following are some of the service operations that
are carried out on components of various suspension
systems.
Compressing strut springs
The coil spring of a strut-type suspension must be
compressed before the strut can be dismantled A
com-pressing tool is fitted over the coils and used to draw
them together.
With most suspensions, the strut can be removed
from the vehicle as an assembly and the compressing
tool used after the assembly has been removed However, in some instances, the compressing tool has
to be fitted to the spring to reduce the length of the strut before it can be removed.
Spring compressing tool
One design of compressing tool is shown in Figure 28.14 This has two pieces Each has a double- ended bolt with a right-hand thread on one end and a left-hand thread on the other These screw into jaws that fit over coils of the spring Screwing the bolts compresses the spring so that the shaft nut can be removed.
figure 28.12 Parts of a McPherson strut for a front
upper spring seat
bump stop
shaft
spring seat
knuckle mounting
figure 28.13 Mountings for a rear strut and spring
1 nut, 2 washer, 3 mounting, 4 insulator, 5 coil
spring, 6 lower spring mounting FORD
4
5
(b) Upper spring seat
(c) Lower spring seat (a) Dismantled strut
(d) Strut mounting—upper
5 6
1 2 3
4
5
6