Buick LeSabre 1965 Service Manual page 234

5 - 2 0 HYDRAULIC CONTROLS
SUPER TURBINE "300'
together. Then both the valve
spring and the pressure of main
line oil against the second land of
the valve will regulate modulator
oil pressure.
e. Governor Valve
The governor valve is a pressure
regulator valve the output of
which is determined by car speed
a c t i n g through the centrifugal
force of a pair of dual weights;
the inner pair of which is spring
loaded. See Figure 5-24.
As the car begins to move the
weight assemblies move outward
to provide a regulating f o r c e
against the v a l v e through the
springs between the primary and
secondary weights. As car speed
is further increased, regulating
force against the valve is pro-
vided by the secondary weights
moving outward. At approximately
35 MPH the primary weights have
reached the limit of their travel
and the force against the valve is
then entirely through the second-
ary weights.
Thus governor valve pressure is
determined at very low speeds by
the primary weights at inter-
mediate speeds by the springs
between the weights and at higher
speeds by the secondary weights.
In this manner governor pres-
sure is increased rapidly but
smoothly from very low speeds
to approximately 40 MPH, where
it increases at a slower rate.
Regulated oil from the governor
valve is channeled to the shift
valve, vacuum modulator valve,
modulator limit valve, and high
speed down shift timing valve.
Governor pressure thus deter-
mines or affects shift points,
main line oil pressure, and down
shift timing.
f. Modulator Limit Valve
The modulator limit valve is a
p r e s s u r e regulator valve that
regulates the point at which a
wide open throttle up shift will
occur.
The valve regulates limited feed
oil (main line pressure) to pro-
vide diminishing oil p r e s s u r e
bearing against the shift control
valve as car speed is increased.
This decrease in oil pressure is
accomplished by governor valve
pressure bearing on the third land
of the valve and acting to diminish
s p r i n g pressure as car speed
(governor v a l v e pressure) in-
creases. See Figures 5-25 and
5-26.
The modulator limit valve is in
operation only before the upshift
during wide open throttle oper-
ation with the manual shift control
valve in Drive position.
[-;
L. FEED 1
-—s
• M M *
_ M 1
Figure 5-26—Modulator Limit Valve
(Second Stage)
g. Detent Valve
The detent valve is a solenoid
operated two position valve that
provides a downshift at wide open
throttle if car speed is low
enough.
Electrical contacts on the carbu-
retor linkage energize the detent
solenoid as wide open throttle is
r e a c h e d . Energization of the
solenoid retracts its plunger and
allows oil from the center of the
valve to flow to exhaust. Main
line oil pressure against the first
land and end of the valve moves
the valve against its spring as
shown in Figure 5-27.
With the valve in this position,
ports are opened to allow oil at
main line pressure flow to the
modulator limit valve and limited
modulator oil to flow to the detent
port of the shift control valve.
When the solenoid is de-energized
the spring loaded plunger seals
the port in the valve center. Oil
Figure 5-24—Governor Valve
Figure 5-25—Modulator Limit Valve
(First Stage)
DETENT VALVE
5 t • ii • ' W I . C I I ^ I D
ENERGIZED
Figure 5-27—Solenoid Valve Energized