Pontiac FIREBIRD 1972 Service Manual page 1052

7G-14 1972 PONTIAC SERVICE MANUAL
Since both the input ring gear and the sun gear are turning
in a clockwise direction at the same speed, the planetary
gear sets are locked and turn as one unit in direct drive
(third gear) or at a ratio of 1 to 1.
In Super (S) range, second gear, the intermediate clutch
is applied to allow the intermediate overrun roller clutch
to hold the drive shell and sun gear stationary (against
counterclockwise rotation). Turbine torque, through the
applied forward clutch, is delivered to the input ring gear
in a clockwise direction (Fig. 7G-10).
Clockwise rotation of the input ring gear causes the output
planet pinions to walk around the stationary sun gear in
a clockwise direction. This causes the output ring gear and
output shaft to turn in a clockwise direction (in a reduc-
tion ratio of approximately 1.52 to 1).
When the transmission is shifted into Super range, the
intermediate overrun band is applied in addition to the
forward and the intermediate clutches. The intermediate
overrun band provides overrun braking, during decelera-
tion or coast, as it holds the sun gear fixed.
With the range selector lever in Low (L) range, the for-
ward clutch is applied (Fig. 7G-11). This delivers turbine
torque from the input shaft through the forward clutch to
the input ring gear in a clockwise direction (converter
torque ratio equals approximately 2.25 to 1 at stall).
Clockwise rotation of the input ring gear causes the output
planet pinions to rotate in a clockwise direction, driving
the sun gear counterclockwise. In turn, the sun gear turn-
ing counterclockwise will cause the output ring gear and
output shaft to turn in a clockwise direction (in a reduc-
tion ratio of approximately 2.52 to 1). The reaction of the
reaction carrier planet pinions against the output ring gear
is taken by the low and reverse roller clutch, which is
grounded to the case, and/or the low and reverse clutch,
which is applied in Low range.
When the selector lever is moved in Low range, the low
and reverse clutch is applied, below a preset controlled car
speed, in addition to the forward clutch which is on for all
forward ranges. The low and reverse clutch provides over-
run braking as it holds the reaction carrier fixed.
With the range selector lever in Reverse (R) range, the
forward clutch is off and the direct clutch is applied to
transmit torque from the forward clutch housing to the
sun gear drive shell and the sun gear. The low and reverse
clutch is applied, preventing the output carrier from turn-
ing (Fig. 7G-12).
Clockwise rotation of the sun gear causes the reaction
carrier planet pinions to turn counterclockwise, turning
the output ring gear and output shaft in a counterclock-
wise direction (in a reduction ratio of approximately 1.92
to 1).
INPUT
OUTPUT
'HELD
REAR G E A R SET
7 .
Intermediate Clutch
-
ON Direct Clutch
-
O F F
Forward Clutch
-
ON
Low and R e v e r s e Clutch
-
O F F
Intermediate Overrun Roller Clutch
-
LOCKED Low and R e v e r s e Roller Clutch
-
FREE WHEELING
Fig. 7G-10 Operation in Super Range
-
Second Gear