CHRYSLER SERVICE MANUAL
TOROUE-FLITE TRANSMISSION—25
valve governor plug and through the ball check
valve to the low-reverse servo.
(2) Through ball check valve to the kick-
down pressure port of the kickdown pressure
port of the 1-2 shift valve kickdown plug.
c. Reverse Blocker Valve
The reverse blocker valve mechanically blocks
the manual valve from moving into reverse
position to prevent accidental reverse engage-
ment above approximately 10-15 mph. When
the reverse button is depressed above this speed
the transmission shifts to neutral and remains
in neutral until another button is depressed.
The reverse blocker valve is activated by gov-
ernor pressure.
d. 1-2 Shift Valve
This valve determines whether the transmission
is either in low gear ratio or second gear ratio,
depending upon whether the valve is in the up-
shifted or down-shifted position. The 1-2 shift
valve train (consisting of shift valve kickdown
plug, valve spring, shift valve and governor
plug) is normally at either extreme of its travel.
With the valve train down-shifted (at the ex-
treme of travel toward the governor pressure
end of the rear valve body) any oil in the kick-
down servo apply area is allowed to escape
through the vent port.
When the shift valve train is moved to the
opposite extreme of its travel, the vent port is
closed off and oil is fed by line pressure to the
following places:
(1) 3-1 relay valve.
(2) Line pressure port of the shuttle valve.
(3) Line pressure port of the throttle com-
pensator valve.
(4) Through servo pressure bleed "D" to
the kickdown servo apply pressure port of the
shuttle valve.
(5) The apply area of the kickdown servo.
(6) The accumulator.
(7) Line pressure port of the 1-2 shift valve
kickdown plug.
The kickdown piston and accumulator are
so designed that the value of the "balance pres-
sure" is sufficient to complete a smooth band
application during the time required to stop the
rear clutch retainer. After completion of the
1-2 shift, the servo apply pressure rises further
to the value of line pressure, providing a "safety
margin" of band load.
At light throttle (low throttle pressure), the
shift valve is made to upshift at approximately
10 mph. and "balance pressure" is at a low
value corresponding to the small force of throt-
tle compensator pressure on the kickdown pis-
ton.
The resulting band application load is,
therefore, in proportion to the light throttle
engine output. At wide open throttle (90 psi.
throttle pressure), the shift valve upshifts at
approximately 40 mph. and throttle compensa-
tor pressure is at a high value, applying the
band at a load corresponding to a high engine
output.
With the 1-2 shift valve train in the upshifted
position, throttle pressure is not allowed to act
on the end of the shift valve. Instead, any oil
trapped in that area is allowed to vent through
the drilled hole in the shift valve. The shift
valve spring then exerts the only force on the
"throttle pressure end" of the shift valve. At
throttle openings less than wide open, the shift
valve will downshift to breakaway when vehi-
cle speed drops to a point where the governor
pressure can no longer overcome the force of
the shift valve spring. This downshift occurs
at a vehicle speed of approximately 7-11 mph.
All that is required of the 1-2 shift valve for
low range operation is that it must downshift
below kickdown limit in response to the move-
ment of the push button to low position and
remain downshifted regardless of vehicle speed.
The shift valve is forced to downshift by the
application of line pressure from the low port
of the manual valve around the ball check valve
to the kickdown pressure port of the 1-2 shift
valve kickdown plug. To insure that the shift
valve remains downshifted regardless of car
speed, line pressure is also allowed to act on-
the low reaction area of the 1-2 shift valve gov-
ernor plug.
It is necessary that whenever the forces of
governor pressure and throttle pressure act on
the shift valve to cause an upshift, the valve
must "snap" from one position to the other
without hesitating or "hunting". This is accom-
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