suspension LAND ROVER DISCOVERY 1999 Owners Manual

REAR SUSPENSION
DESCRIPTION AND OPERATION 64-3
Rear suspension component layout
(vehicles without SLS)
1Coil spring RH
2Damper RH
3Watts linkage
4ACE actuator (if fitted)
5Anti-roll bar link LH
6Coil spring LH
7Damper LH8Torsion/Anti-roll bar
9Radius arm LH
10ACE short arm (if fitted)
11ACE long arm (if fitted)
12Anti-roll bar link RH
13Radius arm RH
14Rear axle

REAR SUSPENSION
64-4 DESCRIPTION AND OPERATION
Rear suspension components
47
44
45
40
3738
39
36
35
34
33
32
23
19
18
1716
M64 0046E
1
2
3
4
5
6
78
910
11
12
13
14
1520
21
22
24
25
26
27
28
29
30
414243
46
48
49
31

REAR SUSPENSION
DESCRIPTION AND OPERATION 64-5
1Rear axle
2Bolt
3Bush
4Locknut
5Transverse link
6Locknut
7Bolt
8Locknut
9Bush
10Bush
11Bolt
12Bolt
13Transverse link
14Bolt
15Bush
16Pivot housing
17Locknut
18Bush
19Lower spring seat 2 off
(vehicles without SLS only)
20Bolt 4 off (vehicles without SLS only)
21Coil spring 2 off (vehicles without SLS only)
22Spring seat isolator 2 off
(vehicles without SLS only)
23Clip 4 off (vehicles with SLS only)
24Air spring 2 off (vehicles with SLS only)25Locknut
26Bush 2 off
27Locknut 2 off
28Radius arm LH
29Locknut
30Torsion/Anti-roll bar link LH
31Washer
32Locknut
33Anti-roll bar assembly
34Mounting rubber 2 off
35Clamp plate 2 off
36Bolt 2 off
37Locknut
38Washer
39Anti-roll bar link RH
40Locknut
41Radius arm RH
42Bush 2 off
43Locknut 2 off
44Locknut 2 off
45Bush 2 off
46Bolt 2 off
47Bolt 2 off
48Bolt 2 off
49Damper 2 off

REAR SUSPENSION
64-6 DESCRIPTION AND OPERATION
Description
General
The rear suspension comprises two dampers, two radius arms, a Watts linkage and an anti-roll bar assembly. On
vehicles without Self Levelling Suspension (SLS) coil springs are used. On vehicles with SLS air springs are used.
The anti-roll bar is an essential part of the rear suspension. On vehicles without ACE, a conventional 'passive' anti-
roll bar is fitted. On vehicles fitted with the ACE system, a thicker diameter anti-roll bar, known as a torsion bar, is used
with an actuator at one end.

+ FRONT SUSPENSION, DESCRIPTION AND OPERATION, Description - ACE.
The hydraulic dampers and springs provide springing for each rear wheel. The long travel dampers, springs and
radius arms provide maximum axle articulation and wheel travel for off-road driving. The rear axle is controlled
longitudinally by two forged steel radius arms and transversely by a Watts linkage.
Radius arms
Each radius arm is manufactured from forged steel. Two bushes are pressed into the rear of the radius arm. The rear
of the radius arm is located between a fabricated bracket on the axle and secured through the bushes with two bolts
and nuts. A bush is pressed into the forward end of the radius arm which is located in a fabricated bracket on each
chassis longitudinal and secured through the bush with a bolt and nut. Each radius arm is similar in its construction
to the front radius arms. The rear radius arms are shorter than the front and have a lug for attachment of the SLS
height sensor (when fitted).
The radius arms prevent longitudinal movement of the rear axle and because of their length allow maximum axle
articulation. The stiffness of the bushes in each radius arm also contributes to the vehicle roll stiffness.
Each radius arm has a notch on its lower edge which provides location for the vehicle jack.
Dampers
Two conventional telescopic dampers are used to control body/axle movement. The upper damper mounting is fitted
with a bush which locates in a bracket on the chassis longitudinal. The damper is secured with a bolt which screws
into a captive nut on the bracket. The lower damper mounting is also fitted with a bush and locates in a fabricated
bracket attached to the rear axle. The lower mounting is secured with a bolt which screws into a captive nut on the
bracket. The upper and lower bushes are replaceable items.
Air springs (vehicles with SLS)
On vehicles with SLS fitted, air springs are fitted between the rear axle and the chassis. Each spring is located at its
base on a fabricated platform on the rear axle. The top of the spring locates in a fabricated bracket attached to the
outside of each chassis longitudinal.
The plastic base of the air spring has two lugs which locate in a slotted hole in the rear axle platform. The spring is
secured by rotating the spring through 90°, locating the lug in the platform. The plastic top of the air spring has two
grooved pins which locate in holes in the bracket on the chassis. Two spring clips locate on the grooved pins and
retain the top of the spring in position.
Each air spring comprises a top plate assembly, an air bag and a base piston. The air bag is attached to the top plate
and the piston with a crimped ring. The air bag is made from a flexible rubber material which allows the bag to expand
with air pressure and deform under load. The top plate assembly comprises the plastic top plate with two bonded
grooved pins on its top face. In the centre of the top face is a female connector which allows for the attachment of the
air hose from the SLS compressor. The piston is made from plastic and is shaped to allow the air bag to roll over its
outer diameter. The base of the piston is recessed with a boss moulded in the centre. The boss has two lugs which
provide attachment to the axle platform.
Coil springs (vehicles without SLS)
On vehicles without SLS fitted, coil springs are fitted between the rear axle and the chassis in place of the SLS air
springs. Each spring is located at its base by the lower spring seat which is secured to a fabricated platform on the
rear axle with two bolts. The top of each spring is located in the upper spring seat. The upper spring seat comprises
a pressed metal plate with an outer coating of natural rubber bonded to the plate. The upper spring seat is retained
in position by the compression of the spring.

REAR SUSPENSION
DESCRIPTION AND OPERATION 64-7
Coil Spring Specifications – Models up to 03 Model Year
The rear coil springs are of the variable rate type and are manufactured from silicon manganese 16.5 mm (0.65 in.)
diameter bar. Each spring has 9 coils and a free length of 385 mm (15.1 in.). The variable rate of the spring is achieved
by the active coils at one end being closer together. The rear coil spring is identified by a purple stripe painted on a
number of coils.
Coil Spring Specifications – Models From 03 Model Year
The introduction of the 03MY vehicle introduced a range of additional rear coil spring fitments. These were introduced
as a package to optimise vehicle trim heights.
The coil springs are manufactured from silicon manganese 16.35 mm (0.64 in.) diameter bar for springs on five seater
models and 16.57 mm (0.65 in.) diameter bar on seven seater models. The following spring data table shows the
colour codes, number of coils and spring free length.
Spring Data
The following table shows spring fitment applicability.
Spring Fitment Applicability
Watts linkage
A Watts linkage is used to ensure that the rear axle remains centrally located. The Watts linkage comprises two
transverse links and a pivot housing. The transverse links and pivot housing allow the rear axle to move vertically
without any transverse movement.
The transverse links are made from fabricated and welded steel. Each transverse link has a bush press fitted into a
housing at one end. The opposite end has a forked bracket with two cross holes.
The pivot housing is made from cast iron. Three bushes are press fitted in the housing, one in the centre and one at
each end.
The pivot housing is located in a fabricated bracket centrally located on the rear of the axle. The central bush of the
pivot housing is secured in the bracket with a bolt and locknut. Fabricated brackets on each chassis longitudinal
provide for the attachment of each transverse link. Each link is secured through its bush with a bolt and locknut. The
forked end of each link locates over the bushes at each end of the pivot housing and is secured with a bolt and locknut.
The attachment bolts for each link are coated with a clear, dry wax which reduces friction on the bolt and allows the
correct torque to be applied to the clamping of the bushes. The bolts can be re-used, but if bolt replacement is
necessary the correct bolt with the wax coating must be used.
Colour Code Total No. of Coils Free Length Model
Brown/Orange 8.73 384.7 mm (15.14 in) 5 Seat
Grey/Orange 8.73 392 mm (15.43 in) 5 Seat
Yellow/Grey 8.73 376.6 mm (14.82 in) 5 Seat
Pink/Grey 8.73 400.3 mm (15.75 in) 5 Seat
Blue/Grey 9.10 387.8 mm (15.26 in) 7 Seat
Green/Grey 9.10 395.2 mm (15.55 in) 7 Seat
White/Grey 9.10 380.6 mm (14.98 in) 7 Seat
Left Hand Drive Right Hand Drive
Both Sides RH Side LH Side
Brown/Orange Grey/Orange Yellow/Grey
Grey Orange Pink/Grey Brown/Orange
Blue/Grey Green/Grey White/Grey

REAR SUSPENSION
64-8 DESCRIPTION AND OPERATION
Anti-roll bar
The anti-roll bars fitted differ between ACE and non-ACE vehicles. On non-ACE vehicles a conventional 'passive' anti-
roll bar is used. On ACE vehicles an 'active' torsion bar is used. Both types are attached to the tubular cross-member
at the rear of the chassis with mounting rubbers and clamp plates. The clamp plates locate in fabricated brackets
attached to the tubular cross-member and secured with bolts.
Each end of the anti-roll bar is attached to an anti-roll bar link. Each link has a spherical bearing attached at each end.
One end is attached to a bracket on the axle and secured with a locknut. The opposite end attaches through a hole
in the anti-roll bar and is also secured with a locknut. On 'active' torsion bars, the RH anti-roll bar link is attached to a
long arm which in turn is attached to the anti-roll bar.
Passive anti-roll bar
The passive anti-roll bar is a conventional anti-roll bar which opposes axle movement, reducing the effects of lateral
forces on the vehicle body.
With the conventional passive anti-roll bar, axle movement is opposed by the anti-roll bar through links attached to
the axle casing and each end of the anti-roll bar.
On vehicles with coil springs (no SLS fitted) the anti-roll bar is manufactured from 19 mm (0.74 in.) diameter spring
steel bar.
On vehicles with air springs (SLS fitted) the anti-roll bar is manufactured from 29 mm (1.14 in.) diameter spring steel
bar.
Active torsion bar

+ FRONT SUSPENSION, DESCRIPTION AND OPERATION, Description - ACE.The 'active' torsion bar is
used in conjunction with the ACE system to control body roll and directional stability giving a reduction of the effects
of lateral forces on the vehicle body over a conventional 'passive' anti-roll bar.
The torsion bar opposes axle movement by the application of a hydraulic force to oppose the lateral forces through
links attached to the axle casing and each end of the bar. The torsion bar is made from 35 mm (1.4 in.) diameter spring
steel. One end is fitted with an arm which is operated by a hydraulic actuator to oppose corning forces.

REAR SUSPENSION
DESCRIPTION AND OPERATION 64-9
DESCRIPTION AND OPERAT ION
SLS component layout
RH drive shown, LH drive similar
1Off-road mode switch
2SLS warning lamp
3Instrument pack
4Off-road mode warning lamp
5RH Height sensor
6RH Air spring7Air inlet filter
8LH Air spring
9LH Height sensor
10Air supply unit
11SLABS ECU

REAR SUSPENSION
64-10 DESCRIPTION AND OPERATION
SLS system control diagram

REAR SUSPENSION
DESCRIPTION AND OPERATION 64-11
1Battery supply (via SLABS relay)
2Ignition supply
3RH height sensor
4LH height sensor
5Off-road mode warning lamp
6Audible warning speaker
7Instrument pack
8SLS warning lamp
9Fusible link 9
10SLS relay
11Air supply unit
12RH air valve
13LH air valve
14Exhaust valve
15Diagnostic socket
16Off-road mode switch
17SLS remote handset
18Body Control Unit (BCU)
19Door switches
20SLABS ECU
21Engine Control Module (ECM)

REAR SUSPENSION
64-12 DESCRIPTION AND OPERATION
Description - SLS
General
The Self Levelling Suspension (SLS) system is an optional fitment and comprises an Electronic Control Unit (ECU),
air supply unit, two air springs and two height sensors. The SLS system only operates on the rear suspension and is
designed to keep the vehicle level to compensate for uneven loads or when towing. The system controls the gap
between the chassis and the rear axle to a tolerance of ± 0.5 mm (0.02 in). The ride height of the rear of the vehicle
can be controlled in three modes of operation; normal ride height, Off-Road Mode (ORM) and extended mode. A
transportation mode, initiated using TestBook, is also available for moving the vehicle on a trailer.
The system is controlled electronically by an ECU which is shared with the ABS system and known as the Self
Levelling and Anti-Lock Braking System (SLABS) ECU. The system operates by using an air supply unit to inflate or
deflate the air springs to maintain a constant ride height.
An accessory remote handset is available to remotely operate the SLS system to allow easier connection and
disconnection of trailers.
Two SLS system warning lamps are located in the instrument pack. The warning lamp in the bottom left corner of the
instrument pack is the SLS warning lamp. If a fault is detected in the system, the warning lamp will illuminate
continuously in an amber colour. The warning lamp also flashes in an amber colour when the remote handset is being
used. The second warning lamp, located in the top right of the instrument pack is the ORM warning lamp. When ORM
is selected the warning lamp is continuously illuminated in an amber colour. When the SLS is between standard ride
height and ORM or in extended mode, the warning lamp will flash. Standard ride height, measured between the tip of
the axle bump stop rubber and the axle, is 61.5 mm (2.42 in). ORM ride height, measured between the tip of axle
bump stop and the axle, is 100 mm (3.93 in).
A switch is located in the group of six switches on the fascia and is used to select the ORM. The switch is non-latching
and must be depressed for a minimum of 0.5 seconds to signal the ECU that ORM has been requested.