Pontiac FIREBIRD 1972 Service Manual page 1055

TURBO HYDRA-MATIC (M-38) TRANSMISSION
7G- 17
modulator, intermediate and reverse pressure (Fig. 7G-
16). It also controls the flow of oil that charges the torque
converter, feeds the oil cooler and provides lubrication
and oil for clutch applications.
MANUAL VALVE
Establishes the range of transmission operation, i.e.,
P, R,
N, D, S and L as selected by the vehicle operator through
the manual selector lever (Fig. 7G- 17).
4
"
1
EXH.
MODULATOR VALVE
Fig. 7G-18 1-2 Accumulator
The modulator valve regulates line pressure to modulator
pressure that varies with torque to the transmission (Fig.
7G-14). It senses forces created by:
1-2 ACCUMULATOR
Line pressure routed to the 1-2 accumulator causes the
piston to cushion application of the intermediate clutch.
The spring within the accumulator acts against the piston.
The force of the spring and the pressure of the 1-2 clutch
oil push the 1-2 accumulator piston back towards the line
oil to allow a gradual build up of the 1-2 clutch pressure
(Fig. 7G-18).
1. The vacuum modulator bellows that increases
modulator pressure.
2. Engine vacuum acting on a diaphragm t o decrease
modulator pressure,
3. Governor pressure which is generated by the gover-
nor assembly. Governor pressure tends t o decrease
modulator pressure.
2-3 ACCUMULATOR
Oil routed to the 2-3 accumulator cushions the application
of the direct clutch. The spring within the accumulator
acts against the piston. The force of the spring and the
pressure of the 2-3 clutch oil push the 2-3 accumulator
piston back towards the R, D, N oil to allow a gradual
build up of the 2-3 clutch pressure (Fig. 7G-19).
1-2 SHIFT VALVE
Routes oil pressure that causes the transmission to shift
from 1-2 or 2-1. Its operation is controlled by governor
pressure, detent pressure, modulator pressure and spring
force (Fig. 7 ~ - 2 0 ) .
Fig. 7G-16 Pressure Regulator Valve
MANUAL VALVE
I
2-3 ACCUMULATOR
Fig. 7G-17 Manual Valve (In Neutral) Fig. 7G-19 2-3 Accumulator