Buick LeSabre 1965 Service Manual page 301

SUPER TURBINE "400' DESCRIPTION & OPERATION 5 - 8 7
Figure 5-210—Governor Assembly
Centrifugal force is proportional
to the square of vehicle speed.
This means that a given change
in vehicle speed results in a
smaller change in governor pres-
sure at low speeds than at high
speeds. Because of this charac-
teristic a governor with a single
weight only is less accurate at
low speed than at high speed. To
increase the accuracy of the gov-
ernor signal at low speeds, the
flyweights are so designed that
their effective mass is greater
at speeds below approximately
720 output RPM than it is above
this speed.
This is done by dividing each fly-
weight into two parts and arrang-
ing them so that the primary
weights act through preloaded
springs on the secondary weights,
which in turn acts on the valve.
At approximately 720 RPM the
centrifugal force on each primary
weight exceeds the spring force
and the primary weights move to
a grounded stop. With the prima-
ry weights grounded, the force
on the governor regulator valve
is equal to the spring forces plus
the centrifugal force on the se-
ondary weights.
Governor pressure acts on the
modulator valve to cause modula-
tor pressure to decrease as vehi-
cle speed increases.
5 - 4 FUNCTIONS OF
VALVE AND
HYDRAULIC
CONTROL UNITS
1. Pressure Regulator
a. Regulates line pressure ac-
cording to a fix«d spring force
and forces controlled by modula-
tor and reverse pressure. See
Figure 5-211.
b. Controls the flow of oil that
charges the torque converter,
feeds the oil cooler and provides
lubrication for the transmission.
2. Manual Valve
Establishes the range of trans-
mission operation, i.e. P, R, N,
D, L
2
, L
1
as selected by the vehi-
cle operator through the manual
selector lever. See Figure 5-212.
m
1
- >
I !
I
5
1
Figure 5-213—Governor Assembly
3. Governor Assembly
Generates a speed sensitive oil
pressure that increases with out-
put shaft or vehicle speed. Gov-
ernor pressure is used to vary
the shift points and modulator
pressure regulation. See Figure
5-213.
4. Modulator Valve
Regulates line pressure to modu-
lator pressure that varies with
torque to the transmission. See
Figure 5-214. It senses forces
created by:
a. The vacuum modulator bel-
low that increases modulator
pressure.
b. Engine vacuum acting on a
diaphragm to decrease modulator
pressure.
Figure 5-211—Pressure Regulator Figure 5-212—Manual Valve
Figure 5-214—Vacuum Modulator
Valve