Buick LeSabre 1965 Service Manual page 293

SUPER TURBINE "400' DESCRIPTION & OPERATION 5 - 7 9
The selector quadrant has six
selector positions: P, R, N, DR,
L
2
, LA
P. - Park p o s i t i o n positively
locks the output shaft to the
transmission case by means of
a locking pawl to prevent the
vehicle from rolling either direc-
tion. This position should be se-
lected whenever the driver leaves
the vehicle. The engine may be
started in park position.
R. - Reverse enables the vehicle
to be operated in a r e v e r s e
direction.
N. - Neutral position enables the
engine to be started and run with-
out driving the vehicle.
DR. - Drive range is used for all
normal driving conditions and
maximum economy.
Drive range has t h r e e g e a r
ratios, from the starting ratio to
direct drive. Detent downshifts
are available for safe passing by
depressing the accelerator to the
floor.
L
2
- L
2
range adds new perfor-
mance for congested traffic or
hilly terrain. L
2
range has the
same starting r a t i o as drive
range, but prevents the transmis-
sion from shifting above second
speed to retain second speed ac-
celeration when extra perfor-
mance is desired. L
2
range can
also be used for engine braking.
L
2
range can be selected at any
vehicle speed, and the transmis-
sion will shift to second gear and
remain in second until the vehicle
speed or the throttle are changed
to obtain first gear operation in
the same manner as in DR. range.
L
1
. - L
1
range can be selected
at any vehicle speed and the
transmission will shift to second
gear and remain in second until
vehicle speed is reduced to ap-
proximately 40 MPH, depending
on axle ratio.
L
1
range position prevents the
transmission from shifting out of
first gear. This is particularly
beneficial for maintaining maxi-
mum engine braking when con-
tinuous first gear operation is
desirable.
a. Neutral—Engine Running
In neutral, all clutches and bands
are released; therefore no power
is transmitted from the torque
converter turbine to the planetary
gear train and output shaft.
b. Drive Range—First Speed
With the selector lever in Drive
Range, the forward clutch is ap-
plied. This d e l i v e r s turbine
torque to the mainshaft and turns
the rear internal gear in a clock-
wise direction. (Converter torque
ratio = approximately 2.:1. at
stall.)
Clockwise motion of the rear in-
ternal gear c a u s e s the rear
pinions to turn clockwise to drive
the sun gear counterclockwise.
In turn, the sun gear drives the
front pinions clockwise, thus
turning the front internal gear,
output carrier, and output shaft
clockwise in a reduction ratio of
approximately 2.5:1. The reaction
of the front pinions against the
front internal gear is taken by the
reaction carrier and sprag as-
sembly to the transmission case.
See Figure 5-200. (Approximate
stall ratio = 5. :1.)
c. Drive Range—Second Speed
In second speed, the intermediate
clutch is applied to allow the in-
termediate sprag to hold the sun
gear against counterclockwise ro-
tation. Turbine torque through the
forward c l u t c h 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 clockwise in a reduction
ratio of approximately 1.5:1. See
Figure 5-201.
d. Drive Range—Third Speed
In direct drive, engine torque is
transmitted to the c o n v e r t e r
through the forward clutch to the
mainshaft and rear internal gear.
Because the direct clutch is ap-
plied, equal power is also trans-
mitted to the sun gear shaft and
the sun gear. Since both the sun
gear and internal gears are now
turning at the same speed, the
planetary gear set is essentially
locked and turns as one unit in
direct drive or a ratio of 1 :1.
See Figure 5-203.
e. Low—L
2
R a n g e -
Second Speed
In second speed, the intermediate
clutch is applied to allow the in-
termediate sprag to hold the sun
gear against counterclockwise ro-
tation. Turbine torque through the
forward c l u t c h is now applied
through the mainshaft to the rear
internal g e a r in a clockwise
direction.
Clockwise rotation of the rear
internal g e a r turns the r e a r
pinions clockwise against the
stationary sun gear. This causes
the output carrier and output shaft
to turn clockwise in a reduction
ratio of approximately 1.5:1.
In second speed, overrun braking
is provided by the front band as it
holds the sun gear fixed. Without
the band applied, the sun gear
would overrun the intermediate
sprag. See Figure 5-204.
f. Low—L
1
R a n g e -
First Speed
With the selector lever in L
1
Range, the forward clutch is ap-
plied. This d e l i v e r s turbine
torque to the mainshaft and turns