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7-48
GROUP 7-AUTOMATIC TRANSMISSION
FIG. 14 - Sectional View of
Torque Converter- Typical
OPERATION
TRANSMISSION
The new transmission features a
drive range that provides for fully
automatic upshifts and downshifts,
and manually selected low and
second gears.
The six selector-lever positions
provided are P (Park), R (Reverse),
N (Neutral), D (automatic Drive
Range), 2 (second-gear hold) and
I (low-gear hold).
Drive (D) is a fully automatic
range providing for a first gear start,
with automatic upshifts to second
and high gear occurring at ap-
propriate intervals. Second gear (2)
is a manually selected second gear
hold. When the selector lever is
moved to (2) the transmission will
engage and remain in second gear,
regardless of throttle opening or
road speed.
D (DRIVE)
The normal automatic driving
range is indicated by D. In this
range the car starts off in first gear
and gives the best combination of
automatic gear shifts, to provide for
economy and fuJi power
starts.
As
the accelerator is depressed and the
car picks up speed, automatic shifts
to second and high gears will occur.
The transmission will automatically
downshift
as
speed
decreases.
Forced downshifts in D are made
by pushing the accelerator to the
floor (kickdown) and the transmis-
sion will shift to 2nd or I st depen-
ding on road speed.
2 (SECOND GEAR HOLD):
When the engine is started and
the shift lever is moved to 2 the cat
will start off and remain in second
gear, regardless of throttle opening
or road speed. This range is
especially useful for starting t.he car
on icy pavements or other shppery
surfaces. Similarly, when engine
braking is required and the selector
lever is moved from D to 2, the
transmission will engage and remain
in
second
gear.
Selector lever
position 2 is not a cruising range in
the usual sense of the term. While
the transmission is capable of
limited cruising in second gear,
maximum fuel economy and best
all-around cruising performance are
realized in D range.
1 (LOW GEAR HOLD):
When the engine is started and
the shift lever is moved to 'I' the
car will start off and remain in first
gear regardless of throttle opening
or road speed.
When I is selected from D or 2
the transmission will engage and
retain first gear when road speed is
below approx. 39 mph.
When I is selected from D with a
road speed above 39 mph second
gear will be engaged and retained
until road speed drops below 39
mph when first gear will be engaged
and retained.
R-Reverse
Reverse gear is selected.
P-Park
In this position the output shaft
is locked to the transmission case
preventing the drive shaft from
rotating. The gear set is in
neutral.
N-Neutral
Places the gear set in neutral but
does not lock the transmission.
TOWING
Important. Should it be necessary
to tow a vehicle fitted with a C4
transmission, the drive shaft must
be disconnected or the rear end of
the car suspended, otherwise subse-
quent failure of the transmission
will occur.
PLANETARY GEAR TRAIN,
CLUTCHES, BANDS,
AND SERVOS
Planetary Gear Train. The gear
train consists of an input shaft that
is splined to the turbine of the
converter and the forward clutch
cylinder(Fig.
l5). The forward clutch
cylinder rotates the steel internal
clutch plates of the forward clutch
and the composition clutch plates
of the reverse-high clutch. When the
reverse-high clutch is applied, the
external area of the clutch hub is
splined to and drives the input shell
to rotate the sun gear. When the
forward clutch is applied, the com-
position clutch plates drive the
forward clutch hub and ring gear.
The ring gear rotates the forward
planet gears.
When applied, the intermediate
band holds the reverse-high clutch
drum, input shell and sun gear from
rotating.
The sun gear, which is driven by
the input shell, is meshed with the
forward and reverse planet gears.
The reverse planet carrier and low
reverse drum are locked together
with external splines. The low-
reverse drum can be held from
rotating by the low-reverse band.
In Dl the low-reverse drum is also
held from rotating by a roller type
one-way clutch.
The forward planet carrier, re-
verse ring gear hub, park gear and
governor oil collector are all splined
to the output shaft.
Forward Clutch. The input shaft
is splined to and drives the forward
clutch cylinder (Fig. 15). Rotation of
the cylinder drives the steel clutch
plates in the forward clutch and the
composition clutch plates of the
reverse-high clutch.
When the forward clutch piston
is applied by hydraulic pressure, the
movement of the piston against the
disc spring locks the steel and com-
position clutch plates together to
drive the forward clutch hub and
ring gear.
When hydraulic pressure is re-
leased from the piston, the disc
spring moves the piston to the
released position. As the disc spring
moves, the steel and composition
clutch plates are released. This stops
the rotation of the forward clutch
hub and ring gear.
The
forward clutch is applied in all
forward drive gear ratios.
Reverse-High
Clutch.
When
hydraulic pressure is directed to the
clutch piston, the piston moves
against the release spring
(Fig.
15).
The piston movement locks the steel
and rotating composition clutch
plates together. The steel clutch
plates drive the reverse-high clutch
drum which is splined to the input
shell. Rotation of the input shell
drives the sun gear which is splined
to the input shell.
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