Pontiac FIREBIRD 1972 Service Manual page 1000

TWO SPEED AUTOMATIC (M-35) TRANSMISSION 7F-13
1
Fig. 7F-19 Oil Pump Priming Valve Circuitry
Fig. 7F-17 Exploded View of Oil Pump
PRESSURE DEVELOPMENT AND CONTROL
Most of the valves and control members of the hydraulic
system are interconnected in some manner and usually
several events are occurring at the same time. In order to
avoid confusion, each components operation will be
treated in a step by step manner.
As oil pump output is being delivered, it is directed
through a passage to an area between spools 2 and 3 of the
pressure regulator valve. This same passage also delivers
oil to the oil pump priming valve (Fig. 7F-19). The prim-
ing valve provides an exhaust for any air that may be
trapped in the system. The priming valve spring holds the
valve in an open position, allowing any trapped air to
exhaust. As the hydraulic pressure builds up in the oil
pump circuit, the valve is forced to seat in its bore, closing
the exhaust bleed hole.
OIL PUMP CIRCUIT
CONVERTER CHARGING CIRCUIT
The internal-external gear type oil pump is driven by the
converter hub. Pump drive is accomplished by two con-
centric tangs machined on the I.D. of the small gear which
engage two matching slots in the converter hub. Since the
converter is bolted to the engine flywheel, the oil pump
operates and provides pressure any time the engine is
running.
As the engine is started and the oil pump begins operating,
fluid is drawn from the sump (oil pan) through a fine mesh
screen and into the suction side of the pump. Output fluid
under pressure enters a passage leading to the area be-
tween two spools of the pressure regulator valve and to the
cavity at the extreme left of the pressure regulator valve
(Fig. 7F-18). Pressure in this cavity causes the valve to
move to the right against spring pressure.
OIL PUMP
As soon as sufficient hydraulic pressure is developed, the
force acting on the left end of the pressure regulator valve
moves the valves to the right against opposing spring force
(Fig. 7F-20). This movement causes the number 2 spool
to uncover the converter feed passage. Fluid in the area
between spools 1 and 2 then fill the converter. The con-
verter is kept fully charged in this way any time the oil
pump is operating and supplying pressure. The converter
is filled through the area between the converter hub and
the stator support by a passage drilled in the oil pump
cover.
Since the converter is continually turning when the engine
is running, the oil is thrown outward and the return loca-
tion is in the area between the input shaft and the inside
Fig. 7F-18 Oil Pump Circuitry Fig. 7F-20 Converter Charging Circuitry