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6-6
SHOCK ABSORBERS
CHASSIS SUSPENSION
(204)
camshaft form the upper control arms of the
front wheel suspension
system.
Right and left shock absorbers are identical
and
interchangeable, however,
calibr at ions
may
differ
between
car mod
els.
Shock absorber cali-
brations for
each
model are gi
ven under
Speci-
fications (par. 6-1) and are also
given
in the
Master Parts List. The
manufacturer's
model
number, coded date of
manufacture,
and the
calibration code numbers are
stamped
on one
end cap of each shock absorber.
The shock absorber body contains a fluid
reservoir connected to two
cylinders
in whi
ch
rebound and compression pistons operate. Both
pistons are fastened together and are simul-
taneously
actuated by a cam located
between
t
heir
inner ends. Th
e
cam is mounted on a
shaft whi
ch
extends through both sides of
the
body and is rotated by the upper control arms
serrated to the outer ends. The rebound
piston
and cylinder are toward the upper arm. See
figure
6-6.
Each
piston is fitted with a spring loaded
valve which
operates
as a main control valve
and also as an inlet valve for return of fluid to
outer end of
the
cylinder. The rebound and
compression
valves
have differ ent calibrations,
whi
ch govern the
rate at which fluid
passes
thr ough
them.
The calibration code
number
is
stamped on
each
valve fo
r proper identifi ca-
tion.
Each compression and rebound val
ve
has a
bleeder
hole
in the val
ve
st em. Under normal
car operation,
when the fluid pressure is ap-
pli
ed by the piston,
transfer of fluid takes place
through
t
he
bleeder hole,
but for violent r
oad
shocks
the
valve
opens
against spring
pressure,
allowing
a
mor e rapid
transfer of
fluid
past
the valve seat
as
well as the
bleed hole.
As the shock ab
sorber
arm
moves downward,
due
to
car spring r
ebound movement, pressure
set
up in the
r
ebound cylinder forces fluid
t
hr ough
t
he
bleeder hole or opens the
rebound
valve by
compressing
the
valve spring ; at
the
same time,
t
he compr ession
valve moves
off
its
seat in the
body, due
to the par t ial vacuum cre-
at ed in the
compression cylinder ,
and the com-
pression cylinder is filled with fluid.
As the
shock
absorber arm moves
up,
pressure
set
up
in t
he compression cylinder forces fluid
through
the bleeder hole
or
opens the compression
valve
by compre ssing the valve spring; at the same
time
,
the rebound val
ve moves
off its seat in
the body, due to the
partial
vacuum cr
eated
in
the
re
bound cylinder,
and the rebound
cylinder
~
is filled with fluid. Thus, the action of the fluid
is the same in both the rebound and
compres-
sion
cylinders,
but the rate of movement of
the
arm up and down is controlled by the size of
the bleeder hole and weight of the spring of
the rebound and compression
valves.
6-6 REAR SHOCK ABSORBERS
Delco double acting, parallel cylinder
type
hydraulic shock absorbers are used on all
mod-
els. Rear shock absorbers are mounted on
t
he
brake backing plates and the arms
are con-
nected to the frame by non-adjustable rubber
bushed steel links. Right and left
rear
sh
ock
absorbers are identical in des
ign
but are not in-
terchangeable. Calibrations for each ca r model
are
given under Specifications (par. 6-1)
and
are also given in the
Master
Parts
List.
Cali-
bration code numbers are stamped on the val
ve
nuts of each shock absorber.
The shock absorber
body
contains a
fluid r
es-
ervoir abo
ve
two
parallel cylinders
in which
compression and rebound pistons operate.
Either piston is mov
ed
downward by a cam
located to bear against the
upper
end
of the
piston
;
while one piston is
being moved down-
ward by the
cam,
the other is
moved upward
by a heavy coil ca p sp
ring. The
cam
is mounted
on a shaft wh
ich
extends through one sid
e
of
the body and is rotated by the sho
ck
ab
sorber
arm
attached
to the
outer
end.
The
compre s-
sion piston and cylinder
a
r e toward the sh
ock
absorber
arm.
See
figur e
6-7.
While
the action
of
t
he
r
ear sh
ock a
bsorbers
is
similar to t
he
f
r ont shock ab
sorbers
(p
ar.
6-5)
,
they a
re
much
faster acting
due t
o t
he
drilled passage
f
rom
one cylinder to
the
other.
Their
construct ion diff
er s
from
the f
ront shock
absorber s as
foll
ows :
1. The oil dis
charge
is from one cylinder to
the other by means of drilled passages in
the
shock
absorber body.
2. The compress ion and r
ebound val
ves
are
located in
the
ends of
the dr illed
passages
rather
than in
t
he
pistons.
The
compression
and r
ebound
valves act
as
main
control
valves
only.
3.
An intake valve is provided in each piston
of the rear shock absorber and its
only
func-
tion is to r
eplenish
fluid lost by piston leakage
as the cylinders are filled under pressure from
valve discharge of opposite cylinder .
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