Page 391
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A. Torque converter
B. Lube
C. Oilpump
ch D. Front clutch
IN? Pressure E, Rear clutch
ey Converter pressure F, Front band
ae Return from secondary G. Front servo
regulator valve
Sept. 1973 SAAB
H.
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N
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‘N" NEUTRAL AND "P” PARK
Rear band
. Rear servo
. Primary regulator valve
. Secondary regulator valve
Strainer
. 2—3 shift valve
- 1—2 shift valve
N<x<CcCHAHMNDO
S 4064
. Servo orifice control valve
. Governor
Manual valve
Downshift valve
. Throttle valve
. Modulator valve
- To oil pan
. Oil cooler (optional)
440-9
Page 392
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440-16
Page 399
Operation of the valves
Primary regulator valve
This valve regulates pump pressure during vehicle opera-
tion.
Line pressure (1), operating on a small area of the valve
can be decreased by modulated throttle pressure (8) (de-
scribed later) operating on one end of the valve. These
forces are opposed by the primary regulator valve spring
and throttle pressure (9) (described later) operating on
the spring end of the valve. The line pressure thus pro-
duced varies with accelerator position as well as vehicle
speed and provides the correct clutch and brake band
capacity under all operating conditions. The line pres-
sure (1) is directed to the manual valve and throttle valve.
Secondary regulator valve
This is a regulating valve which controls the values of con-
verter pressure (21) and lubrication (23) for the compo-
nents in the rear of the transmission case. Converter pres-
sure operating on one end of the valve is opposed by
spring force on the other end. When the pump capacity
increases due to increased engine speed, the valve moves
to open a port that directs fluid (24) to the suction side
of the pump. Thus, at high speed, excess pump output is
directed back to minimize pumping losses.
Downshift valve and throttle valve
The downshift valve is connected to the carburetter link-
age via a cable-actuated cam. Movement of the downshift
valve compresses the throttle valve spring located between
the downshift valve and the throttle valve. This spring is
opposed by the throttle return spring, combined with
throttle pressure (9) acting (at low vehicle speed) on one
area of this regulating valve, and at high speed on two areas
(9 and 9a). Thus a throttle pressure is produced that is
related to both engine torque and vehicle speed. This pres-
sure (9) is directed to the spring end of the primary regu-
lator valve to vary the basic line pressure (1) accordingly,
thus providing correct clutch and brake band capacities
and appropriate shift quality under all operating condi-
tions.
Full movement of the downshift valve, which is a shuttle
valve, directs throttle pressure (11—9) to the 2—3 shift
valve and the 1—2 shift valve to further delay upshifts or
effect a 3—2 downshift or a 2—1 downshift at a Preset
maximum vehicle speed.
Sept. 1973
Throttle pressure (9) is directed also to the 2—3 shift
plunger which at part throttle openings reduces the value
of throttle pressure by a fixed amount. This reduced pres-
sure (10) is directed to the 1-2 and 2—3 shift valves to
render the low speed shift points less sensitive to throttle
pressure and, therefore, accelerator position. Throttle pres-
sure (11—9) is also directed to the 1—2 shift valve enabling
a 3—1 downshift to be made at a preset speed.
Modulator plug and valve
The modulator plug is a regulating valve that reduces
throttle pressure (9) by a fixed amount. This modulated
pressure (8) operating on one end of the plug, assisted by
the modulator valve spring, is opposed by throttle pres-
sure (9) operating on the opposite end. Modulated throt-
tle pressure (8) is directed to the primary regulator valve
to vary the rate of increase of line pressure (1) relative to
throttle pressure.
The modulator valve is a shuttle valve. Governor pressure
(2) operating on the large end is opposed by the modula-
tor valve spring. As governor pressure rises, the valve moves,
preventing the plug from regulating and modulated throt-
tle pressure (8) then becomes equal to throttle pressure
(9). Moreover this movement directs throttle pressure (9 and
9a) to a second area of the throttle valve opposing throttle
valve spring force. This arrangement permits high throttle
and line pressure under stall (and part-throttle) conditions
with a reduction in these pressures after “cut-back’’.
Servo orifice control valve
A common line (15) supplies fluid to, or exhausts fluid
from, the rear clutch and the release area of the front
servo to effect the 2—3 and 3—2 shift.
The servo orifice control valve is a shuttle valve interposed
in the front servo release circuit. Governor pressure (2)
operating on an area of the valve is opposed by the valve
spring. At a 2—3 shift with low governur pressure (i.e. low
vehicle speed), fluid goes without restriction to the release
side of the front servo piston, At a 2—3 shift with higher
governor pressure, however, the valve moves and fluid is
directed through an orifice to this side of the piston.
During upshifts, with the servo orifice in circuit, the front
band does not release too quickly relative to rear clutch
engagement, thus avoiding “run-up” during the transition
from 2 to 3. During downshifts, the orifice in circuit en-
sures that the front band does not engage before the rear
clutch releases thus avoiding ‘‘tie-up"’ on the 3—2 shift.
The servo orifice contro! valve, therefore, affects the rela-
tionship between the rear clutch and front servo to pro-
vide correct shift timing under all operating conditions,
440-17
Page 400
1—2 shift valve and plunger
Both are shuttle valves and operate in unison in "D’ and ‘2’
selector positions. In 1st gear governor pressure (2), oper-
ating on the large end of the valve, is opposed by line pres-
sure (5) operating on an area of this valve, the 1—2 shift
valve spring and reduced throttle pressure (10—10a) oper-
ating on the opposite end of the plunger. When governor
pressure exceeds these opposing forces, the valve moves
to the 2nd gear position and line pressure (5) is directed
to the apply side of the front servo piston (19). The move-
ment also results in an area of the valve being no longer
subjected to line pressure (5). This allows the 2—1 down-
shift to occur at a lower speed than the 1—2 shift. The
difference between the upshift and downshift speed is
known as "shift point hysteresis’. When governor pres-
sure is less than the spring force combined with the re-
duced throttle pressure force, the valve moves to the 1st
gear position and the apply side of the front servo (19)
is opened to exhaust (x).
In ‘1'-Lock-up, with low governor pressure (2) the valve
also moves to the 1st gear position; line pressure (6) thus
directed to the rear servo (13) latches the valve hydrauli-
cally in the 1st gear position, preventing an upshift.
Forced throttle pressure can cause the 1—2 shift valve to
give a 3—1 downshift below 30 m.p.h. (50 km/h) in the
‘D’ range or a 2—1 downshift in the ‘D’ or ‘2’ range.
2-3 shift valve and plunger
The 2—3 shift valve plunger is a regulating valve that re-
duces the value of throttle pressure (9) by a fixed amount
and therefore is inoperative when throttle pressure is below
this fixed amount. Throttle pressure (9), operating on one
end of the plunger, is opposed by this reduced throttle
pressure (10) and the 2—3 shift valve spring located be-
tween the plunger and valve. This reduced pressure is direct-
ed to the 2—3 shift valve and the 1—2 shift plunger as de-
scribed under “ Downshift and throttle valve’.
The 2—3 shift valve is a shuttle valve. In the 2nd gear po-
sition, and before the plunger begins regulating, governor
pressure (2), operating on the large end of the lve, is
opposed by line pressure (3) operating on an area of this
valve, as well as the 2—3 shift valve spring. Once the plung-
er begins regulating, the spring no longer exerts a force on
the valve but relays the force of the plunger to the valve.
Under these conditions, governor pressure (2), operating
on the large end of the valve, is opposed by line pressure
(3) operating on an area of the valve, reduced throttle
pressure (10) operating on the small end of the valve, and
throttle pressure (9) operating on the end of the plunger.
This last force is relayed to the 2—3 shift valve by the
valve spring.
Movement of the shift valve to the 3rd gear position di-
rects fluid via the common line (15) to the rear clutch and,
440-18
via the servo orifice control valve, to the release side of
the front servo. This pressure causes the rear clutch to be
applied. Moreover, because the release area of the front
servo is larger than the apply area it causes the front band
to be released. The movement also results in an area of
the valve being no longer subjected to line pressure (3);
this movement prevents regulation of the plunger forced
to the end of the valve bore. Thus reduced throttle pres-
sure (10) is replaced by throttle pressure (9). This change
in forces effects the shift point hysteresis and causes the
3—2 shift point to occur at a lower governor pressure (i.e.
vehicle speed) than the 2—3 upshift.
When the manual valve is moved to the ‘2’ position line
pressure (15) which was directed to the 2—3 shift valve
and consequently to the rear clutch and front servo release,
is exhausted (7) through a port (x) at the opposite end of
the manual valve collar. This inevitably results in an im-
mediate downshift to 2nd gear regardless of the position
of the 2—3 shift valve and no third gear is possible.
In Reverse, line pressure (7) is directed to the rear clutch
and front servo release (15).
Manual control valve
This valve, actuated by movement of the selector, directs
line pressure to, or exhausts from, the appropriate valves
or components in accordance with control requirements.
P: Movement of the valve mechanically engages the
parking pawl with the externally toothed ring gear on the
driven shaft, effectively immobilising the vehicle. No
fluid is directed to the front clutch or 2—3 shift valve for
the rear clutch, therefore the gear set is disconnected from
the converter and no engine power is transmitted to the
wheels. Because of the arrangement of the manual con-
trol valve ports for other selector positions, line pressure
(6) is directed to the rear servo (13).
R: Line pressure (6) is directed to the rear servo (13) via
the 1—2 shift valve and also (7) to the rear clutch (15) via
the 2—3 shift valve. No pressure is directed to the gover-
nor.
N: The clutches and servos are not pressurised and ex-
hausted, because circuits 3 and 5 are open to a port (x)
nearest to the manual control valve collar. Therefore the
gear set is disconnected from the converter and no engine
power is transmitted to the wheels.
D: Line pressure (5) is directed to the front clutch, gover-
nor and 1—2 shift valve. It is also directed to the 2—3
shift valve. When there is sufficient governor pressure, it
passes without obstruction to the 1—2 shift valve.
2: Line pressure (5) is again directed to the front clutch,
governor and 1—2 shift valve. Governor pressure is directed
to the 1—2 shift valve.
1: Line pressure (5) is directed to the front clutch, gover-
nor and 1—2 shift valve. Line pressure (6) is directed to a
differential area of the 1—2 shift valve to lock it in position
and hence to the rear servo (13).
Sept. 1973