Advertisement
7-6
GROUP
7- AUTOMATIC TRANSMISSION
ernor pressures, front servo release
fluid goes direct to the release side
of the front servo piston.
At
higher governor pressures the valve
moves and fluid is directed through
an orifice and then to the release
side of this piston.
A
common
line supplies fluid to,
or exhausts fluid from, the rear
clutch and the release area of the
front servo, to effect the second to
third and third to second change.
At low speeds, when the servo
orifice is by-passed, the front servo
releases quickly with the result
that second to third or third to
second changes are smooth
.
At
higher speeds, the front servo re-
lease fluid passes
through
the ori-
fice which delays the front servo
release and effects a firm second
to third and third
to
second change.
The servo orifice control valve
therefore affects the relationship
between the rear clutch and front
servo to provide correct change
quality under all operating con-
ditiom
Shift Valve Operation-
'D'
Selected
First to Second Valve and
Plunger.
Both the first to second valve
and plunger are shuttle valves and
operate
together
when
"D"
is se-
lected. Governor pressure, operat-
ing on the large end of the first to
second valve, is opposed by reduced
throttle pressure from the second
to third plunger and the spring
operating on the opposite end of
the first to second plunger. When
the governor pressure exceeds the
spring force combined with re-
duced throttle pressure, the valve-
moves tn the second 2ear oosition
and control pressure is directed to
the apply side of the front servo
piston.
Movement of the valve
removes control pressure from an
additional area of the valve and
exhausts reduced throttle pressure
from
the plunger via the downshift
valve.
This allows the change from
second
to
first to occur at a lower
speed than the change from first to
second. When governor force is less
than
the
spring
force, the valve
moves to the first gear position and
the apply side of the front servo is
opened
to
exhaust.
Second to Third Vah·e and
Plunger.
The second to third plunger is
a
regulating
valve
that
reduces the
value of throttle pressure by a fixed
amount and is inoperative when
throttle pressure is below this fixed
amount.
Throttle pressure, oper-
ating on one end of the valve
plunger is opposed by this reduced
throttle pressure and the second to
third valve spring located between
the plunger and valve.
This re-
duced pressure is directed to the
second to third valve and the first
to second plunger to vary the
change points sensitivity relative to
throttle pressure and accelerator
position.
The second to third valve is a
shuttle valve.
In the second gear
position and before the second to
third valve plunger begins regulat-
ing, governor pressure, operating
on the large end of this valve is
opposed by the second to third valve
spring.
Mter the plunger begins regulat-
ing, governor pressure, operating on
the large end of the valve, is opposed
by reduced throttle pressure opera-
ting on the small end of the valve,
and throttle pressure operating on
the end of the second to third valve
plunger. The latter force is relayed
to the second to third valve by the
valve spring. Movement of the valve
to the third gear position directs
fluid to the rear clutch and the
release side of the front servo
through the servo orifice control
valve. This pressure applies the rear
clutch. Since the release area of the
front servo is larger than the apply
area, the front servo and therefore,
front band is released. This move-
ment also results in an area of the
valve being no longer subjected to
control pressure and prevents regu-
lation of the second to third valve
plunger by forcing the plunger to
the end of the valve bore. Therefore
reduced throttle pressure which was
acting on the small end of the valve
is exhausted at the downshift valve.
This change in forces causes the
third to second change to occur at a
lower governor pressure, and there-
fore road speed, than the second to
third change.
THIRD TO SECOND DUMP
VALVE
The valve allows a quick down-
change from top to second gear to
take place when
2
or 1 is manually
selected.
The operation consists of by-
passing the orifice restriction in the
rear clutch and front servo release
hydraulic line with a one way ball
valve. The ball is held in position on
the separator plate with a very light
spring.
HYDRAULIC CIRCUITS AND
POWER FLOW
"N" Neutr•l (Refer Fig. 10).
With the engine running the
primary regufator valve regulates
control pressure which is directed
to the manual valve and throttle
valve and it also permits fluid to
reach
the
secondary
regulator
valve.
The secondary regulator valve
regulates pressure to the conver-
ter and lubrication of the front
end ot the transmission. The same
pressure is directed to the rear end
ot the transmission.
The valve returns excess ftuid
to the
oil pan through the pump
inlet.
No power is transmitted
since the clutches and bands are
released.
First Gear with "D" selected.
Hydraulic Circuits
Pressure control of the pump
will be as with "N".
However,
with the downshift valve
cam
in
the full throttle position, throttle
pressure regulated by the modula-
tor valve plunger acts upon the
primary reglf'lator val\1! opposing
throttle pressure, thus modulating
control pressure for change quality.
The manual valve directs con-
trol pressure to the front clutch,
first to second valve and governor
feed. Control pressure reaches the
second to third valve to provide
for the subsequent second to third
change.
Power Flow.
The front clutch is applied con-
necting the converter turbine
to
the forward sun gear.
The one-
way clutch operates so preventing
the pinion carrier from rotatina
anti-clockwise.
The ring
gear,
connected to the output shaft, is
rotated through the planets at an
overall ratio of 2.39 to 1. When
the car coasts the one way clutch
overruns and the gearset free-
wheels so that engine brakina is
not available.
Second Gear with "D" selected.
Hydraulic Circuits
Change control is provided by
the first to second valve movina
Advertisement
