Pontiac FIREBIRD 1972 Service Manual page 915

TURBO HYDRA-MATIC (M-40) TRANSMISSION 7E-25
POWER FLOW
Forward Clutch
-
Applied
Roller Clutch
-
Effective
Direct Clutch
-
Released
Front Band
-
Released
Rear Band
-
Released
Intermediate Clutch
-
Released
Intermediate Sprag
-
Ineffective
Detent Solenoid
-
De-energized
DRIVE RANGE-FIRST GEAR
With the selector lever in any forward range, the forward
clutch is applied. This delivers turbine torque to the main-
shaft and turns the rear internal gear in a clockwise direc-
tion, viewed from front (Converter torque ratio equals
approximately 2:l at stall).
Clockwise motion of the rear internal gear causes the rear
pinions to turn clockwise, driving the sun gear counter-
clockwise. In turn, the sun gear drives the front pinions
clockwise, thus turning the front internal gear, output
carrier and output shaft clockwise in a reduction ratio of
approximately 2.5: 1.
Reaction of the front pinions against the front internal
gear is taken by reaction carrier and roller clutch assembly
to the transmission case (Approximate stall ratio equals
5:l).
OIL FLOW
When the selector lever is moved to Drive position, the
manual lever is repositioned to allow line pressure to enter
the drive circuit. Drive oil then flows to the:
1. Forward Clutch
2. 1-2 Shift Valve
3. Governor Assembly
4. 1-2 Accumulator Valve
5. Detent Regulator Valve
BASIC CONTROL
Drive oil is directed to the forward clutch where it acts on
two areas of the clutch piston to apply the forward clutch.
The inner area is fed through an unrestricted passage. The
outer area is fed through an orifice to insure a smooth shift
from Park, Neutral and Reverse to Drive.
Drive oil at the governor assembly is regulated to a varia-
ble pressure. This pressure increases with vehicle speed
and acts against the ends of the 1-2 and 2-3 shift valves and
an area on the modulator valve. This variable pressure is
called governor pressure.
Drive oil is also regulated to another variable pressure at
the 1-2 accumulator valve. This pressure, called 1-2 ac-
cumulator oil, is controlled by modulator oil and is di-
rected to the rear servo. 1-2 accumulator oil at the rear
servo acts on the accumulator piston.
SUMMARY
The converter is filled and the forward clutch is applied. The transmission
is in Drive range
-
first gear.
DRIVE RANGE-SECOND GEAR
POWER FLOW
Forward Clutch
-
Applied
Roller Clutch
-
Ineffective
Direct Clutch
-
Released
Front Band
-
Released
Rear Band
-
Released
Intermediate Clutch
-
Applied
Intermediate Sprag
-
Effective
Detent Solenoid
-
De-energized
In second gear, the intermediate clutch is applied to allow
the intermediate sprag to hold the sun gear against coun-
terclockwise rotation. Turbine torque, through the for-
ward clutch, is applied through the mainshaft to the rear
internal gear in a clockwise direction:
Clockwise rotation of the rear internal gear turns the rear
pinions clockwise against the stationary sun gear. This
causes the output carrier and output shaft to turn clock-
wise in a reduction ratio of approximately 1.5:l.