Buick LeSabre 1965 Service Manual page 306

5 - 9 2 DESCRIPTION & OPERATION SUPER TURBINE "400'
L O.
DRIVE
n j
1-9
DET. MOD.
JL II
ACCUMULATOR
Figure 5-237
f . Rear Servo Operation-
Reverse Range
In Reverse the rear band is ap-
plied to hold the reaction carrier.
Reverse oil is directed to the
servo piston to apply the band.
To insure the band holding the
reaction carrier for the reverse
gear ratio, line pressure is in-
creased in Reverse and no other
oil pressures are present in the
servo to resist the apply of the
servo piston. See Figure 5-236.
16. 1-2 Accumulator
1-2 Accumulator oil charges the
rear servo accumulator in 1st
gear in preparation for the apply
of the intermediate clutch on the
1-2 shift.
The valve train consists of a 1-2
primary valve and spring, a 1-2
accumulator valve and spring and
a 1-2 accumulator adjusting plug
and screw.
1-2 Accumulator oil pressure is
a two-stage pressure to obtain
greater flexibility in obtaining the
desired curve for various engine
requirements.
Drive oil is directed to the 1-2
accumulator valve and is regu-
lated by the valve train to 1-2
accumulator oil. Modulator pres-
sure is directed to the primary
valve and its effect is on the
primary and 1-2 accumulator
valve for the first stage of 1-2
accumulator p r e s s u r e . When
modulator pressure on the larger
area of the primary valve can
overcome the effect of modulator
pressure and spring pressure on
the smaller area of the primary
valve, it moves the primary valve
to its stop and increases the ef-
fective area for modulator pres-
sure on the 1-2 accumulator
valve which results in 1-2 pres-
sure rising faster to start the
second stage of 1-2 accumulator
pressure. The result of these two
stages of 1-2 accumulator pres-
sure is that at light throttle
shifts, 1-2 accumulator pressure
is on a lower pressure slope for
smooth shifts and on heavy throt-
tle shifts, 1-2 accumulator pres-
sure is on the second slope of
higher pressures for s m o o t h
durable shifts.
Detent oil is directed to the 1-2
primary valve to raise 1-2 ac-
cumulator pressure during detent
1-2 shifts for clutch durability.
Lo Range oil is directed to the
1-2 accumulator valve during Lo
Range operation to raise 1-2 ac-
cumulator pressure to line pres-
sure; t h i s increased pressure
directed to the rear servo ac-
cumulator piston resists servo
apply pressure and slows down
the apply of the rear band for a
smooth manual shift to Lo Range
1st gear or for a 2-1 shift in Lo
Range.
L O
LpBK
B i —
i
. DRIVE
LTL J j
-
1
1.9
DET. MOD.
JL 1
ACCUMULATOR
LO. DRIVE DET. MOD.
1-2 ACCUMULATOR
Figure 5 - 2 3 8
Figure 5 - 2 4 0
The 1-2 accumulator pressure is
adjusted by the adjusting screw
at the factory and should not be
changed in field service.
a. 1-2 Accumulator-1st Stage
Drive oil is regulated to 1-2 ac-
cumulator pressure by the effect
of modulator oil and spring pres-
sure on the primary and 1-2
accumulator v a l v e s and 1-2
accumulator oil and spring pres-
sure on the 1-2 accumulator
valve. The lo passage is used for
exhaust.
In the first stage of regulation the
primary valve is grounded to the
1-2 accumulator valve and the
effective area on which modulator
pressure is working is small,
which results in a low slope of
1-2 accumulator pressure. See
Figure 5-237.
b. 1-2 Accumulator 2nd Stage
When modulator pressure on the
larger area of the primary valve
can overcome modulator oil and
spring pressure on the smaller
end of the p r i m a r y valve, it
grounds the primary valve in the
valve bore. This results in a
larger effective area for modula-
tor pressure to work on, and 1-2
accumulator pressure is on the
higher slope. See Figure 5-238.