Pontiac FIREBIRD 1972 Service Manual page 920

7E-30 1972 PONTIAC SERVICE MANUAL
DETENT DOWNSHIFT
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
-
Energized
Drive oil on the detent regulator valve is then regulated
to a pressure of approximately 70 psi and called detent oil.
Detent oil is then routed to the:
1. Modulator Passage
2. 1-2 Regulator Valve
3. 2-3 Modulator Valve
4. 3-2 Valve
In second gear, the intermediate clutch is applied to allow
5. 1-2 Primary Accumulator Valve
the intermediate sprag to hold the sun gear against coun-
terclockwise rotation. Turbine torque, through the for-
6. Vacuum Modulator Valve
ward clutch, is now applied through the mainshaft to the
rear internal gear in a clockwise direction.
Detent oil in the modulator passage and at the 2-3
modulator valve will close the 2-3 valve, shifting the trans-
Clockwise rotation of the rear internal gear turns the rear
mission to second gear (below approximately 70 mph).
w
pinions clockwise against the stationary sun gear. This
causes the output carrier and output shaft to turn clock-
A detent 2-1 downshift can also be accomplished below
wise in a reduction ratio of approximately 1.5:l.
approximately 20 mph because detent oil is directed to the
1-2 regulator valve. This allows detent oil to act on the 1-2
OIL FLOW
regulator and 1-2 detent valve to close the 1-2 shift valve,
shifting the transmission to first gear.
While operating at speeds below approximately 70 mph,
To insure clutch durability during 1-2 upshifts under de-
a forced or detent 3-2 downshift is possible by depressing
tent conditions, detent oil is directed to the 1-2 accumula-
the accelerator fully. This engages an electrically operated
tor primary valve to increase 1-2 accumulator oil pressure
switch and actuates the detent solenoid. The detent solen-
acting on the rear servo accumulator piston.
oid opens an orifice that allows line oil at the detent valve
to be exhausted, thus permitting the detent regulator valve
Detent oil is also directed to the modulator valve to pre-
to operate. Line oil acting on the detent valve and solenoid
vent modulator pressure from regulating below 70 psi at
is supplied by a small orifice.
high speed or at high altitudes.
PART THROTTLE DOWNSHIFT
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 now 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 ration of approximately 1.5: 1.
OIL FLOW
A part throttle 3-2 downshift can be accomplished below
approximately 33 mph by depressing the accelerator far
enough to raise modulator pressure to approximately 105
psi. Modulator pressure and the 3-2 valve spring will move
the 3-2 valve against direct clutch oil and allow modulator
oil to act on the 2-3 modulator valve. This moves the 2-3
valve train against governor oil and shifts the transmission
to second gear.