Pontiac FIREBIRD 1972 Service Manual page 294

4-8 1972 PONTIAC SERVICE MANUAL
Fig. 4-6 Typical Leaf Spring Rear Suspension
commercial chassis and all F & X Series consists of two
leaf springs and two sealed shock absorbers mounted be-
tween the spring lower seats (anchor plates) and frame (B
Series station wagon and commerical chassis) or under-
body floor pan (F & X Series). B & F Series are equipped
with multiple leaf springs. A single leaf spring is standard
on the X Series and a multiple leaf spring is utilized with
special performance suspension. F
&
X Series have stag-
gered shock absorbers with the right shock absorber in
front and left shock absorber behind the axle housing
tubes. Staggering the shock absorbers reduces spring
wrap-up during acceleration and braking. Both shock ab-
sorbers are placed in front of the axle housing tubes on B
Series station wagons and commercial chassis. The springs
are rubber mounted at the axle and frame side rail (B
Series) or underbody side rail (F Series) attaching points,
thus ensuring uniform spring loading, minimizing trans-
mittal of road vibration to passenger compartment and
providing a pivot point to absorb axle wind-up. The
springs are positioned to the axle spring seats by a locating
bolt placed close to the center of the spring.
Rubber bumpers are mounted near the outer ends of the
axle housing and at the center on a bracket bolted to the
front of the differential assembly (B Series) or bolted to the
underbody (F
&
X Series) to prevent metal-to-metal con-
tact during compression travel or bottoming of the sus-
pension.
SHOCK ABSORBERS
STANDARD AND HEAVY DUTY
Double acting standard and heavy duty shock absorbers
are filled with a calibrated amount of fluid and sealed
during production. They are non-adjustable, non-refilla-
ble and cannot be disassembled. The only service they
require is replacement if they have lost their resistance, are
damaged or leak oil. See Section 3 for operation and diag-
nosis of standard and heavy duty shock absorbers.
A dampener (weight) is added to the single leaf spring on
X Series models without special performance suspension.
This weight is strapped 10" rearward of the spring front
eye bushing and its purpose is to dampen out excessive or
unwanted spring oscillations.
A steil stabilizer shaft is used to improve side roll stability
on Formula and Trans Am models (Fig. 4-7). A steel
stabilizer shaft is also used on X Series with special per-
formance suspension. The shaft ends are mounted in rub-
ber insulators supported by brackets bolted below each
spring and shock absorber anchor plate. Two supports
(struts) connect the shaft to the underbody side rails. Each
support lower end clamps around a rubber bushing on the
stabilizer shaft and the upper end contains a pressed-in
rubber, bushing for attaching by a pivot bolt to a U-shaped
bracket welded below the underbody side rail in the kick
up area. The support and pressed-in rubber bushing are
not serviced separately, but only as an assembled unit.
The Superlift system is an assist-type leveling device
which the owner controls manually by varying air pres-
sure in the system. The leveling unit is a combination of
a pliable neoprene boot and air cylinder built around a
hydraulic shock absorber (Fig. 4-8). As an integral part of
the rear suspension, it offers the car owner added load-
carrying flexibility. A level ride can be maintained when
carrying abnormal loads by merely increasing air pressure
in the system. When load is removed, the car can be
lowered to its normal riding height by decreasing air pres-
sure. Air pressure is adjusted by means of a tire-type valve
conveniently located in the rear bumper area except B
Series station wagons and commercial chassis which have
the valve located on the top right side of the radiator
support and baffle assembly. Since one valve serves both
units, air pressure is equal at all times. Superlifts are avail-
able on B Series.
LEVELING UNIT
The Superlift leveling unit is mounted in the same location
as a conventional rear shock absorber. The units are de-
signed so that shock absorber function is not impaired in
the event of accidental air loss.
FILL VALVE ASSEMBLY
A fitting at'the rear bumper or on B Series station wagons
and commercial chassis at the top right side of the radiator
support and baffle assembly contains a tire-type valve
which provides a means of filling the shocks with air and
exhausting air from the shocks.