Pontiac FIREBIRD 1972 Service Manual page 912

7E-22 1972 PONTIAC SERVICE MANUAL
into the modulator passages. The detent valve train also
routes detent pressure into the detent passages to the shift
valve trains. The upshift points are then controlled by
detent pressure in the modulator passages and the detent
downshifts by detent pressure in the detent passages.
These shift points are fixed at relatively high speeds by the
constant pressure.
Detent pressure is directed to the 1-2 accumulator pri-
mary valve to increase 1-2 accumulator pressure for clutch
durability during detent shifting. Detent pressure is di-
rected to the modulator valve to prevent modulator pres-
sure from dropping below approximately 70 psi which, in
turn, prevents line pressure from dropping below approxi-
mately 105 psi.
In Lo range operation, Lo oil is directed to the detent
regulator valve and spacer. The spring then moves the
detent and regulator valves to the opposite end of the valve
bore (Fig. 7E-24). Lo oil is also directed to the detent
regulator valve to a passage which is used as an exhaust
when the valve is regulating. Lo oil in these two areas
prevents the detent valve from regulating and drive oil
passes through the detent regulator valve into the detent
and modulator passages at Lo range pressure of 150 psi.
This increase in detent and modulator pressures will
downshift the 1-2 valve at speeds below approximately 40
mph and will prevent the transmission from upshifting out
of first gear, regardless of vehicle speed.
NEUTRAL RANGE-ENGINE IDLING
POWER FLOW
Forward Clutch
-
Released
Roller Clutch
-
Ineffective
Direct Clutch
-
Released
Front Band
-
Released
Rear Band
-
Released
Intermediate Clutch
-
Released
Intermediate Sprag
-
Ineffective
Detent Solenoid
-
De-energized
In Neutral or Park, no bands or clutches are applied.
Therefore no power is transmitted.
OIL FLOW
Whenever the engine is running at idle with the selector
lever in P or N, oil from the pump is directed to the:
5. Detent Solenoid
6. Vacuum Modulator Valve
7. Front Servo (Neutral only)
BASIC CONTROL
Oil flows from the pump to the pressure regulator valve
which regulates pump pressure. When the pump output
exceeds the demand of line pressure, oil from the pressure
regulator is directed to the converter feed passage to fill
the converter. Oil from the converter is directed to the
transmission cooler. Oil from the cooler is directed to the
transmission lubrication system.
Line pressure acts on the:
1. Manual Valve
2. Detent Valve
1. Pressure Regulator Valve
3. Detent Solenoid
2. Converter:
a. Oil Cooler
4. Modulator Valve
5. Front Servo Piston (Neutral Only)
b. Lubrication System
3. Manual Valve
4. Detent Valve
Line pressure at the modulator valve is re-regulated to
modulator oil, which acts on the pressure boost valve and
1-2 accumulator valve train and passes through the detent
valve and 3-2 valve to the 1-2 and 2-3 valve trains.
S U M M A R Y
The converter is filled and all clutches and bands are released. The trans-
mission is in Neutral or Park.