Advertisement
PART 7-3- F. M.X. AUTOMATIC TRANSMISSION
7-101
REAR SERVO
LOCKOUT VALVE
The six passages that connect to
the rear servo lockout valve are pres-
surized as follows:
1. Rear Clutch Apply Pressure
2. Exhaust
3. Rear Servo Apply Pressure
4. 1-R·P Pressure From Manual
Valve
5. Rear Servo Apply Pressure
6. D Pressure From Manual Valve
When the transmission is operating
in D range, line pressure from the
manual valve is directed through the
2-lshift orifice ball check valve to the
bottom of the rear servo lockout
valve; this pressure holds the valve in
the upward position against the force
of front clutch apply pressure and
spring effort at the top of the valve.
While the valve is in this position, line
pressure from the D passage of the
manual valve is prevented from pres-
surizing the rear servo apply circuit.
When the selector lever is in the R
position, R fluid from the manual
valve is directed through the 2-3 shift
valve to the area differential at the
lower valley of the rear servo lockout
valve; the force resulting from this
pressure assists the spring in keeping
the valve downward in its bore, so
that servo apply pressure can pass
through the bore and pressurize the
servo apply
circuit.
THROTTLE REDUCING
VALVE
Before throttle pressure or boosted
throttle pressure is admitted to the
front face of the 2·3 shift valve, plug
and 1-2 shift valve, it must open a
passage past the spring-loaded throt-
tle reducing
valve.
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 valve 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£ ore, be re-
duced.
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 rest (closed) posi-
tion by springs. It is opened by gover-
nor pressure. Under various driving
conditions, governor pressure is op-
posed by spring force plus throttle
or boosted throttle
pressures,
and con-
trol
pressure.
INHIBITOR VALVE
The inhibitor valve prevents a 2-1
downshift, either manual or
kickdown,
at excessive road speeds
.
The inhibitor valve is held in its
rest (open) position by a
spring.
It is
closed by governor pressure
.
Under
various driving conditions, governor
pressure is opposed by spring force
plus control pressure.
1-2 SHIFT ACCUMULATOR
AND LOCKOUT VALVES
Four passages connect to the bore of
the 1-2 shift accumulator and lockout
valves
;
from left to right the first pas-
sage is connected to direct-reverse
clutch apply pressure through the 3-2
kickdown control valve and its orifice;
the second is connected to the release
side of the intermediate servo, the
third is connected
.
to the upper valley
of the 1-2 shift valve and
the
fourth is
connected directly to direct-reverse
clutch apply
pressure.
The 1-2 shift
accumulator and lockout
va
lves con-
trol the quality of the 1-2 shift
by
regulating the servo apply force as
follows
:
To make a complete servo applica-
tion,
apply pressure must stroke the
servo piston against the force of the
release spring, and at the same time
force out the fluid in the release side
of the
servo.
Fluid from the release
side of the servo unseats the check
ball to bypass the intermediate servo
release orifice and is then routed to
the valley of the 1-2 shift accumulator
valve. As pressure builds up in the
apply side of the servo causing the
servo piston to stroke toward the apply
position, a similiar pressure build-up is
transmitted through the piston to the
release circuit and acts on the area
differential of the 1-2 shift accumula-
tor valve
;
this will force the valve to
the left against its spring until the
left-hand passage is uncovered, allow-
ing the fluid in the release side of the
servo to escape to exhaust at the
manual valve. In this way servo
a
pply
force is reduced to the required level
by regulating a back pressure on the
release side of the servo.
When the transmission upshifts to
high gear, direct and reverse clutch
apply pressure is routed to the right-
hand passage behind the 1-2 shift ac-
cumulator lockout
va lve, a
nd through
the check valve and 3-2 kickdown
control valve to the valley of the 1-2
shift accumulator valve
;
the entire
shift accumulator and lockout
valve
train moves to the left
a
nd is held
there
insuring that the release sid
e
of
the intermediate
servo
will be pres-
surized whenever the transmiss ion is
in high
gear.
In addition, should the
accelerator pedal be depressed to
force
a
kickdown into second
gea r,
the shift accumulator
va
lve will re-
main to the left so that clutch
a pply/
servo release fluid
ca
n flow without
obstruction to the 3-2 kickdown con-
trol
valve,
where the
exha
ust of this
fluid is controlled
.
When
the
transmission
selector
lever is moved from D to 2 or I to
provide engine braking, line pressure
from the 2-1
-
R-P passage is directed
through the 1-2 shift valve to the
third port of the 1-2 shift accumu-
lator valve at the end adjacent to the
lockout valve. The force produced by
this pressure acting on the end of the
valves moves the valve to the left, keep-
ing it in that position. This insures
that servo release pressure will be
quickly exhausted through the direct
and reverse clutch circuit, permitting
an immediate band application.
DOWNSHIFT VALVE
Three passages intersect the bore of
the downshift valve. The left-hand pas-
sage is vented to exhaust
;
the middle
passage is connected to the adjacent
ends of the 2-3 throttle reducing valve
and 2-3 shift delay
valves
and to the
inhibitor valve. The third passage of
the downshift valve is connected to the
D passage of the manual
valve.
When the car is in intermediate or
high gears (G:ive range) and the
ac-
celerator pedal is floored, to force
the downshift valve in against spring
force, the '!?.lvc seals off the exhaust
port and rcat.:s line pressure from the
manual valve to the inhibitor valve
and to the adjacent ends of the 2-3
throttle reducing. valve and 2-3 shift
delay
valve,
tending to move the 2-3
shift valve upward in its
bore.
If the
force due to governor pressure acting
on the area differential at the lower
valley of the 2-3 shift valve is suffi-
ciently low the valve will move up-
ward and the transmission will engage
second gear. At the same
time,
down-
shift pressure is directed from the
Advertisement
