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. (099)
PART 7-2-TURBO-DRIVE AUTOMATIC TRANSMISSION
7-19
low 51 psi, therefore, throttle pres-
sure will flow through the boost valve
without interference.
Throttle pressures above 51 psi
will move the boost valve to the right
(Fig. 7). This movement will first
cut off throttle pressure flow to the
shift valves and coasting control
valve, and it will then open a pas-
sage to permit control pressure to
enter the throttle pressure circuit. The
new boosted throttle pressure is di-
rected to the shift valves and the
coasting control valve. Throttle pres-
sure will continue to work against
the end of the boost valve. For each
pound of increase in throttle pres-
sure (above 51 psi), the boosted
throttle pressure will increase about
three pounds.
GOVERNOR PRESSURE
Governor pressure is produced
from control pressure from the front
clutch circuit by the valve in the
governor body which rotates at out-
put shaft speed.
The governor valve is a balanced
valve. It is balanced between centrif-
ugal force acting on the governor
valve plus governor spring force and
governor pressure force (Fig. 7).
Governor pressure is, therefore, pro-
portional to road speed.
TRANSITION VALVE
The transition valve controls the
front servo apply pressure flow.
In the D 1 range, the transition
valve blocks front servo apply pres-
suite flow until the 1-2 valve is closed
by governor pressure.
In the D2 range, the transition
valve permits front servo apply pres-
sure to flow through it at all times.
1-2 SHIFT VALVE
The 1-2 shift valve controls the
1-2 upshift in the Dl range. On the
2-1 downshift, either manual (shift
to L) or kickdown, the 1-2 shift
valve controls the shift only within
the road speed range permitted by
the inhibitor valve.
The 1-2 valve is held in its open
position by a spring. It is closed by
governor pressure. Under various
driving conditions, governor pres-
sure is opposed by spring force plus
reduced throttle and reduced boosted
throttle pressures, and control pres-
sure.
THROTTLE REDUCING VALVE
Before throttle pressure or boosted
throttle pressure is admitted to the
face of the 2-3 shift valve and 1-2
shift valve, it must open a passage
past the spring-loaded valve (Fig. 7).
Approximately 20 psi throttle pres-
sure is required to move the valve
against its spring far enough to open
the passage. Once past the valve,
throttle pressure will work on the
spring end of the plug and exert a
force to cut off throttle pressure flow
past the valve. In this case, the valve
becomes a balanced valve wherein
the valve is balanced between
throttle pressure force on the one
end and spring force plus throttle
pressure force on the other end. The
pressure past the valve will, there-
fore, be reduced.
2-3 SHIFT VALVE
The 2-3 shift valve controls the
2-3 upshift and the 3-2 downshift.
The valve is held in its closed posi-
tion by springs. It is opened by
governor pressure acting on the end
of the valve. Under various driving
conditions, governor pressure is
opposed by spring force plus throttle
or boosted throttle pressures, and
control pressure.
INHIBITOR VALVE
The inhibitor valve prevents a 2-1
downshift, either manual or kick-
down, at excessive road speeds.
The inhibitor valve is held in its
open position by a spring.
It
is closed
by governor pressure. Under various
driving conditions, governor pres-
sure is opposed by spring force plus
control pressure.
3-2 COASTING CONTROL
VALVE
The 3-2 coasting control valve.
operates in the front servo release
passage.
During a 3-2 closed-throttle down ..
shift in D2 range, the valve is posi ..
tioned by its spring so that front
servo release pressure must exhaust
slowly through an orifice. This slow
exhaust of release pressure provides
a slow front band application.
During
a
partial-to-full-throttle
3-2 downshift, the 3-2 coasting con-
trol valve is positioned by throttle
pressure or boosted throttle pressure
so that front servo release pressure
can exhaust rapidly to provide a
rapid front band application.
DOWNSHIFT VALVE
The downshift valve is in the con-
trol valve upper body. The inner
downshift lever contacts one end of
the spring-loaded downshift valve.
Control pressure is directed to a
land of the valve. Linkage is con-
nected between the accelerator pedal
and downshift lever. The downshift
valve is moved to open a passage
to direct control pressure to the shift
valves and the inhibitor valve when
the accelerator pedal is depressed
through the detent (Fig. 7).
3-2 KICKDOWN CONTROL
VALVE
The 3-2 kickdown control valve
operates in the front servo release
pressure' passage between the 2-3
shift valve and the front servo. A
check valve is installed parallel with
the kickdown control valve in the
same passage so that release pressure
flow to the servo by-passes it.
The kickdown valve controls the
rate of front servo release pressure
exhaust (flow from the servo), and
thereby the rate of front band ap-
plication.
The 3-2 kickdown control valve
eliminates the possibility of a run-
away condition in the transmission
during a 3-2 kickdown at low car
speeds (about 25 mph).
It
also elimi-
nates the possibility of a tie-up during
the same shift at higher speeds (50
mph and more) .
REVERSE SHUTTLE VALVE
When the transmission is shifted
to reverse, rear servo apply pressure
is directed to the reverse shuttle valve
(Fig. 7) . In addition, rear clutch
apply pressure is also directed to the
reverse shuttle valve where it acts
on the area provided by the differ-
ence in the diameters of the lands
of the valve. As the rear clutch is
applied, pressure builds up in this
circuit until the pressure force on the
valve provided by rear clutch apply
pressure
overcomes
the
reverse
shuttle valve spring force. At this
point the valve moves against spring
force, blocking the rear servo ex-
haust passage and allowing rear
servo apply pressure to pass through
the shuttle valve and apply the rear
servo and band. In this manner, the
rear band application is timed with
the rear clutch application when re-
verse ratio is selected.
In Park position, rear servo apply
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