Pontiac FIREBIRD 1972 Service Manual page 903

TURBO HYDRA-MATIC (M-40) TRANSMISSION
7E- 13
PLANET GEARS
PLANET CARRIERS
(REACTION CARRIER) (OUTPUT CARRIER1
Fig. 7E-5 Compound Planetary Gear Set
The torque converter couples the engine to the planetary
gears through oil and provides hydraulic torque multi-
plication when required. The compound planetary gear set
produces three forward speeds and reverse (Fig. 7E-5).
The 3-element torque converter consists of a pump or
driving member, a turbine or driven member and a stator
assembly. The stator is mounted on a one-way roller
clutch which will allow the stator to turn clockwise but
not counter-clockwise when viewed from the front (Fig.
7E-6).
The torque converter housing is filled with oil and is at-
tached to the engine crankshaft by a flex plate, thus always
rotates at engine speed. The converter pump is an integral
OIL STATOR CONVERTER
FLOW. ASSEMBLY PUMP
TURBINE
ROLLER
CLUTCH
- -
-
STATOR TURBINE
OIL F L O W SHAFT SHAFT
part of the converter housing, therefore the pump blades,
rotating at engine speed, set the oil within the converter
into motion and direct it to the turbine, causing the tur-
bine to rotate.
As the oil passes through the turbine, it is traveling in such
a direction that if it were not re-directed by the stator it
would hit the rear of the converter pump blades and im-
pede its pumping action. So, at low turbine speeds, the oil
redirected by the stator to the converter pump in such a
manner that it actuallly assists the converter pump to
deliver power or multiply engine torque.
As turbine speed increases, the direction of the oil leaving
the turbine changes and flows against the rear side of the
stator vanes in a clockwise direction. Since the stator is
now impeding the smooth flow of oil, its roller clutch
releases and it revolves freely on its shaft. Once the stator
becomes inactive, there is no further multiplication of
engine torque within the converter. At this point, the
converter is merely acting as a fluid coupling as both the
converter pump and turbine are being driven at approxi-
mately the same speed
-
or at me-to-one ratio.
A hydraulic system, pressurized by a gear-type pump,
provides the working pressure required to operate the
friction elements and automatic controls. External control
connections to transmission are:
Manual Linkage
-
To select the desired operating range.
Engine Vacuum
-
To operate a vacuum modulator unit.
12 Volt Electrical Signal
-
To operate an electrical detent
solenoid.
Approximate gear or torque ratios of the transmission are
as follows:
First
-
2.5 gear ratio
x
2 converter
stall ratio
..........................................................
5:l
*Second
-
1.5 gear ratio
......................................
1.5:1
*Third
..................................................................
1 :1
Reverse
-
2:l gear ratio X 2 converter
............................................................
stall ratio 4:l
*Second and third are also multiplied.
A vacuum modulator is used to automatically sense any
change in the torque input to the transmission. The
vacuum modulator transmits this signal to the pressure
regulator for line pressure control, to the 1-2 accumulator
valve and to the shift valves so that all torque require-
ments and shift speed requirements of the transmission are
met and smooth shifts are obtained at all throttle open-
ings.
Fig. 7E-6 Converter Operation
The detent solenoid is activated by an electric switch on
the firewall. When the throttle is fully opened, the switch