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7-54
GROUP 7-AUTOMATIC TRANSMISSION
end
of the pressure
booster valve.
When force
created
on the booster
valve by
T.V.
pressure or T.V. and
coasting boost pressure exceeds
pressure booster valve
spring
force,
the
force
will be added to the main
regulator valve spring
force
trans-
mitted to the
regulator
valve. This
will provide
increased
line pressures
required
to
compensate for in-
creased
throttle
openings and
~r\gine
torque output.
Figure
19
shows
how
line pressure
varies
with engine
vacuum at 0 output shaft rpm.
(R Range)
In
reverse,
additional fluid pres-
sure
is required
to prevent clutch
and/or band
slippage
under stall or
partial stall conditions. This addi-
tional pressure
is
provided by direct-
ing R oil pressure to the middle
valley of the pressure booster valve.
The differential in area between the
lands creates a force which is added
to the
forces
present due to T.V.
pressure and the line coasting boost
valve pressure. The resultant force
is added
to
the force of the main
regulator valve
spring,
to boost line
pressure to a higher value than is
available in the forward driving
ranges.
GOVERNOR
At Rest-O mph
Control pressure (line)
is
fed to
the
secondary
governor valve
through the center passage in the
valve
body when a forward range
has been
selected.
Because of the
differential
in area of
the
inner
and
outer lands
of
the
valve.
the valve
will be
forced inward, shutting
off
line
pressure
feed to the. governor
passage and allowing this passage
to be
opened
to exhaust, at the inner
end
of
the
valve.
At the same time,
line
pressur.e will
pass by two flats
on the
outer
end of the
valve,
pres-
surizing the
line leakage passage
leading
to the primary governor
valve. At
rest,
the spring on the
outer end of
the primary governor
valve
holds the
primary
governor
valve
inward,
blocking
further
flow
of
the fluid in the
line leakage pas-
sage. This causes
pressure
in
the line
leakage passage to build to the same
value
as
line
pressure. As a conse-
quence, the
secondary
governor
valve
is
held
in and
there
is no
pres-
sure
in the
governor
circuit.
Above 10 mph
When vehicle speed reaches ap-
proximately 10
mph,
centrifugal
force on the primary governor valve
overcomes spring force, and the
valve moves outward, opening the
line leakage passage to exhaust.
This action reduces the pressure on
the end of the secondary governor
valve to zero (0), allowing the
secondary valve to also move out-
ward, due to spring force and
centrifugal force. When the secon-
dary valve moves outward, it
closes
the governor exhaust passage, and
allows line pressure to enter the
governor passage. As pressure builds
in the governor passage
it
will create
a force on the secondary governor
valve due to the differential in areas
of the inner and outer lands of the
valve. This force tends to move the
valve inward. When the force on
the valve created by pressure in the
governor passage exceeds the centri-
fugal force plus spring force, the
valve will move inward, allowing
governor pressure to exhaust, and
close the passage between line pres-
sure and governor pressure. When
governor pressure is reduced, the
secondary valve will again move
outward, closing the governc:: ex-
haust port and opening the line
pressure to governor passage. Above
10 mph, governor pressure
is
regu-
lated in this manner, and will vary
with vehicle speeds.
If vehicle speed drops below I 0
mph, the primary valve spring will
move the primary governor valve
in, closing the line leakage exhaust
port at the primary valve. Pressure
in the line leakage passage will be-
come equal to line pressure, forcing
the secondary governor valve in.
This action shuts off line pressure
feed to the governor passage and
exhausts the governor circuit.
When the secondary governor
valve is regulating, governor pres-
sure will be delivered to the cut-
back valve, end of the 2-3 shift
valve and the I -2 shift valve. Figure
21
shows the relationship between
governor pressure and output shaft
rpm.
100
:;
..:
60
20
0
0
10
15
20
25
30
OUTPUT SHAFT RPM•100
Dl559·A
FIG. 21 - Govemor Pressure
Versus Output Shaft RPM
THROTTLE
BOOSTER
VALVE
Note: While
the throttle booster valve
is
fitted to all
C4
transmissions it is
rendered ineffective on transmissions
fitted to 250
C.I.D.
2V and 302
C.I
.D.
2V engines by a ball inserted in
the
booster
valve spring preventing
valve movement.
Throttle
plate openings above
50°
provide
very little change in
engine
vacuum as compared to
throttle plate opening below 50°.
The
throttle booster
valve
is pro-
vided to boost throttle pressure and
provide
the necessary
shi~t
delay for
engine throttle plate opemngs above
50°.
Below
approximately 60 psi pri-
mary
T.V. pressure, T.V. pressure
flows
to and through the throttle
boost
valve unaffected, working on
the end of
the boost valve and on
the area differential on the spring
side of
the
boost valve. As a con-
sequence,
T.V.
pressure
passes
through
the throttle boost valve
unaffected.
When
T.V. pressure increases
above 60
psi,
the force created by
·
T.V. pressure
acting on the end of
the throttle boost valve, minus the
force of
T.V. pressure acting on the
area differential
on the spring side,
will exceed the force of the spring.
This
causes the valve to move
against the spring, closing off pri-
mary
T.V. pressure to the area dif-
ferential
on the spring side and
permitting
this area to be fed from
line pressure,
causing a boost in the
pressure used
for shift delay only.
Because
the area of the end of the
throttle boost
valve exceeds the area
differential
on the spring side by
approximately
2! to I, throttle
boost pressure
above 60 psi primary
T.V. pressure
will increase 2.5 psi,
per
I
psi
primary T.V.
T.V.
pressure from the throttle
booster
valve is delivered to the
downshift
valve, throttle modulator
valve, cut-back valve, and spring
end of the 2-3 backout valve.
Figure 19 shows the relationship
between
primary T.V. pressure and
boosted
throttle pressure.
THROTTLE
MODULATOR
VALVE
The throttle modulator valve,
located
in the end of the 2-3 shift
valve
bore,
reduces throttle pres-
sure which acts on the ends of the
2-3
shift valve and on the area dif-
ferential
of the 1-2 shift valve.
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