Ford COUGAR 1968 Shop Manual page 255

PART 7-3
-
C6
Automatic Transmission
introduced between the 1-2 shift and
D2 valves. This action opens the D2
valve and holds it open, providing a
second gear start and preventing a
2-1 downshift.
Intermediate Servo Accumulator
a n d Capacity Modulator Valves
The intermediate servo accumula-
tor and capacity modulator valves are
used to control the rate of band ap-
plication during a 1-2 shift.
During operation in first gear
prior to the 1-2 shift, line pressure
on the lower end of the servo ac-
cumulator valve holds the valve upward
in its bore against the force of spring
.
-
pressure.
When the 1-2 shift valve train
moves downward in the bore; signal-
ling an upshift into 2 range, line pres-
sure is directed from the D2 shift valve
to the intermediate servo capacity
modulator valve. This pressure passes
thru the capacity modulator valve bore,
goes to the differential in area be-
tween the two lands of the accumula-
tor valve and thru the 2-3 backout
valve to apply the intermediate servo.
This same fluid also passes thru a
hole in the center of the capacity
modulator valve to the end of the
valve, and also thru an orifice which
feeds the fluid to the spring ends of
the accumulator and capacity modu-
lator valves.
The fluid which passes thru the
center of the intermediate servo ca-
pacity modulator valve tends to move
the valve upward against spring force.
However, the spring effort and fluid
pressure created by the fluid which
has passed thru the orifice t o , the
spring end of the valve will hold
the valve down.
As fluid flows thru the orifice to
the spring ends of the accumulator
and capacity modulator valves, and
pressure increases on the spring ends
of the valves, the accumulator valve
starts to move downward. This move-
ment of the accumulator valve causes
a flow of fluid thru the orifice, result-
ing in a lower pressure existing on
the spring sides of the valves.
As a consequence, the fluid pres-
sure on the end of the capacity mod-
ulator valve opposite the spring will
be higher than the pressure on the
spring end of the valve, causing the
valve to move upward. This action
cuts off fluid supply to the intermedi-
ate servo (and thru the orifice) and
opens an exhaust port at the end of
the capacity modulator valve. When
the exhaust port opens, the pressure
on the end of the capacity modulator
valve opposite the spring is reduced,
allowing the valve to again move
downward and opening the line to the
intermediate servo apply.
In this manner, the intermediate
servo capacity modulator valve regu-
lates to control the intermediate
servo apply during a 1-2 shift, until
the intermediate servo accumulator
valve has fully bottomed in its bore
and there is no more fluid flow thru
the orifice.
2-3 Shift Valve
The 2-3 shift valve is held closed
by throttle modulator valve spring
force, modulated throttle pressure
force, and by D fluid pressure force
acting on the differential in area of
the lands of the valve to which it is
delivered.
Governor pressure tends to open
the 2-3 shift valve. When force
created by governor pressure ex-
ceeds the forces holding the valve
closed, the valve will move down-
ward (open) closing the exhaust
passage (through the manual valve)
and opening the D passage to al-
low D fluid to apply the reverse-
high clutch and release the inter-
mediate servo.
With the shift valve open (down)
the throttle modulator valve is held
down cutting off modulated throttle
pressure to the 2-3 shift valve and
1-2 shift valve. In addition, the port
which delivered D fluid to the dif-
ferential in area of the shift valve
lands, is closed.
The shift valve will be reopened
(moved up) causing a downshift un-
der one or more of the following
conditions:
Governor Pressure Reduced. If
governor. pressure is reduced to the
point where it can no longer hold the
shift valve down against spring force,
the valve will move up causing a
downshift. Under closed throttle
conditions, the 2-3 shift valve will
close a t approximately 10 mph,
(speed a t which governor pressure is
cut off). Since governor pressure is
cut off a t this speed, the 1-2 shift
valve train also closes a t the same
time. This will provide a 3-1 down-
shift when coasting in D range.
Throttle Pressure Increased. If
throttle pressure is increased suffi-
ciently, it will move the throttle
modulator valve and consequently
the 2-3 shift valve up, causing a 3-2
torque demand downshift.
Line Pressure Introduced Below
2-3 Shift Valve. If the downshift
valve is moved through detent, line
pressure is directed to the underside
of the 2-3 shift valve, forcing the
valve up and causing a forced 3-2
downshift. Maximum 3-2 forced
downshift speed is controlled by gov-
ernor pressure.
In addition to the above, a 3-2
downshift will occur when the man-
ual valve is moved to 1 range. The
D passage which feeds fluid to the
2-3 shift valve will then be opened
to exhaust, allowing reverse-high
clutch apply-intermediate servo re-
lease fluid to exhaust and causing a
3-2 downshift.
2-3 Back-out Valve
The purpose of the 2-3 back-out
valve is to provide smooth upshifts,
when the throttle is suddenly closed
while accelerating in second gear.
Operation is as follows:
Normal Throttle-On 2-3 Upshifts.
When the 2-3 shift valve moves to
cause a 2-3 upshift, D fluid passes
through the valve to apply the direct
clutch and release the intermediate
servo. This same fluid is also directed
to the end of the 2-3 back-out valve.
However, with throttle open, pri-
mary throttle pressure on the oppo-
site end of the 2-3 back-out valve,
assists spring force in holding the
valve up, so that there will be no
valve movement until after the 2-3
shift has been completed.
Back-Out 2-3 Upshifts. When the
throttle is closed during a 2-3 up-
shift, and before the shift is com-
pleted, there may be enough pres-
sure in the reverse-high clutch cylin-
der to apply the clutch at the re-
duced engine torque input, but not
enough pressure to release the inter-
mediate servo. This condition could
cause a harsh 2-3 shift. However, if
the throttle is closed during a 2-3
shift, primary throttle pressure will
be reduced to zero (0). and reverse-
high clutch apply pressure on the
end of the 2-3 back-out valve will
move the valve down against spring
force. This action immediately con-
nects the clutch apply circuit to the
intermediate servo apply circuit, re-
ducing the pressure on apply side of
the servo to the same value a s in the
reverse-high clutch (and also on the
release side of the intermediate ser-'
vo). When this happens, the inter-
mediate band is released, to provide
a smooth 2-3 shift.