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REAR SUSPENSION
30-25
SUPERLIFT
-
LEAK TEST
See SHOCK ABSORBER DIAGNOSIS in Section 3 of
this manual.
GENERAL DESCRIPTION
Automatic Level Control (ALC), available as a factory
or dealer installed option on B Series, automatically
maintains the rear standing height of the car at a nearly
constant position, regardless of load changes. The system
consists of an air compressor, reservoir and pressure regulator
assembly (Fig. 3D-33), height control valve, link, two
Superlift rear shock absorbers and flexible air lines.
Fig.
30-33
Compressor Assembly
The automatic level control (ALC) compressor is a two-
stage, vacuum activated type and requires no lubrication. The
compressor converts manifold vacuum taken from the
positive crankcase ventilation hose into air pressure which is
retained in the reservoir. As reservoir pressure drops due to
ALC system air usage, the compressor begins to recycle and
replenish reservoir air pressure. The pressure regulator valve
is preset and limits reservoir outlet pressure to approximately
125 psi to avoid damage to the height control valve and/or
Superlift shocks.
An air filter located on the compressor should be
inspected periodically to see if it has become plugged.
HEIGHT CONTROL VALVE
The height control valve, which is mounted on the
frame, senses rear car height through a link attached to the
right rear upper control arm. When load is added to the car,
the over-travel lever is forced up causing an internal lever to
open the intake valve. When this valve is open, high pressure
air is admitted to the Superlift shocks. As the car raises to
level, the intake valve shuts off.
When load is removed from the car, the over-travel lever
is forced down causing the internal arm to open the exhaust
valve. As the car lowers to the level position, the exhaust
valve shuts off.
A 4-1 8 second time delay mechanism, which is built into
the height control valve, prevents air transfer due to normal
ride movements. The over-travel lever, which pivots around
the control valve shaft, rides off the flat side of the control
valve shaft and does not have time to react to the rapid
changes or normal ride motions.
During changes due to loading, the time delay
mechanism will allow the over-travel shaft to open either the
intake or exhaust valve as required, since this is not a rapid
movement.
SUPERLIFT SHOCK ABSORBER
The Superlift shock absorber used with ALC will extend
when inflated and retract when deflated by the height control
valve. Each unit is connected to the control valve by a
common flexible air line. The common line equalizes air
pressure in the two Superlifts.
An 8-15 psi air pressure is maintained in the Superlift
at all times to minimize boot friction. This is accomplished
by a check valve in the exhaust fitting on the control valve.
Neither shock absorber *function nor conventional ride
motions through the rear suspension springs is impaired in
the event of accidental air pressure loss.
Shock absorbers do not require lubrication and in case
of leaks or malfunction, they should be replaced.
LINES A N D FITTINGS.
Flexible air lines are used throughout the system. The
line is 1/8" diameter tubing. Each fitting consists of a rubber
seal, metal sleeve and nut. These parts are intended
specifically for the 1/8" diameter line and must be used to
affect a reliable seal.
NOTE: While the lines are flexible for easy routing and
handling, care should be taken not to kink them and to
keep them from coming in contact with the exhaust
system.
ON-CAR SERVICE
Precautions
The precautions outlined below should be heeded to
insure satisfactory function of the system:
MINIMUM
PRESSURE
For
best
ride
characteristics with an empty car, a minimum pressure of 10
psi should be maintained.
0
MAXIMUM PRESSURE
-
the pressure may be varied
to a maximum of 90 psi to level the car with loads.
0
LINES A N D FITTINGS
-
The air lines cannot
withstand exhaust system temperatures. At least 1 1/2"
clearance should be maintained between the air lines and any
portion of the exhaust system.
0
Flexible air lines are used throughout the system and
are 1/8" diameter tubing. Each fitting consists of a rubber
seal, metal sleeve and nut (Fig. 3D-21). These parts are
intended specifically for the 1/8" diameter line and must be
used to affect a reliable seal.
0
While the lines are flexible for easy routing and
handling, care should be taken not to kink them and to keep
them from coming in contact with the exhaust system (Fig.
3D-34).
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