•
TRANSMISSION
21 -
1
TRANSMISSION
CONTENTS
page
FLUID
TEMPERATURE
THERMO-SWITCHES
.
2
GENERAL
INFORMATION
1
GENERAL
SPECIFICATIONS-DIESEL A518
...3
GOVERNOR
WEIGHT
ASSEMBLY
1
PLANETARY
GEARS
1
SERVICE
PROCEDURE
AND
SPECIFICATION
CHANGES
2
SERVICING THE
NEW
OVERRUNNING
GENERAL
INFORMATION
A
heavy duty version of the A518,
4-speed
auto-
matic
transmission
has
been released for use
with
the Cummins turbo diesel engine.
Major
differences between diesel and
gas
engine
versions of the A518
involve
the:
•
transmission
case
•
torque converter
•
planetary
gears
•
transmission shafts
•
governor weight assembly
•
overrunning clutches
•
fluid
temperature thermo-switch
TRANSMISSION
CASE
The diesel A518 transmission
case
has
a
larger
converter housing to accommodate the 12.2
in.
torque
converter. The housing
bolt
pattern
is
also different
being
drilled
for the Cummins engine block.
TORQUE COUVERTER
A
three element, non-lockup torque converter
is
used for diesel engine applications. Converter diame-
ter is 12.2 in. (310 mm).
The converter
is
not
a
serviceable component. Re-
place the converter
as
an assembly if diagnosis
indi-
cates
this is
necessary.
TRANSilSSiON
0VERRU1N1NG
CLUTCH
AND
LOW-REVERSE
DRUM
A
new design overrunning
clutch
is used in diesel
versions
of
the A518 transmission. The
individual
components consist of: the cam,
which
is
still
pressed
into
the
case;
the
clutch
race
which
is
now
pressed
onto the hub of the low-reverse drum; and the new
cage-type overrunning
clutch
assembly.
The
new overrunning clutch assembly
will
also
be phased into gasoline engine versions
of
the
A727/A518
transmission. Production release
is
scheduled for sometime in
January
or
February
1991.
page
CLUTCH
•i3Q1330i3COOUyjiOOOt)»300B3B 2
TORQUE
CONVERTER
. ... 1
TRANSMISSION
AND
OVERDRIVE
COMPOUNDER
CLUTCH
PACKS
1
TRANSMISSION
CASE
1
TRANSMISSION
OVERRUNNING
CLUTCH
AND
LOW-REVERSE
DRUM
1
The new
clutch
assembly contains more rollers and
springs than previous models. It also features
a
cage-
type
retainer for the springs and rollers. The
sepa-
rate retainer used previously is eliminated.
The
clutch
race
is now
pressed
onto the hub of the
low-reverse drum. The
race
is
not removable and
is
serviced
only
as
part of the drum.
The new
clutch
cam is essentially the
same
as the
prior
design. The tools and service techniques for re-
placing
new and
prior
design
clutch
cams
are the
same.
Refer
to the
procedures
in
Group 21 of the
1991
manual.
PLANETARY
GEARS
The transmission and overdrive planetary
gear
car-
riers
in the diesel A518 are heavy duty components.
The transmission planetary carriers have
four
pin-
ion
gears.
The carrier in the overdrive compounder
has
five
pinion
gears.
The heavy duty planetary
units
are unique to the diesel version of the A518.
TRANSMISSION
AND
OVERDRIVE
COMPOUNDER
CLUTCH
PACKS
Clutch
packs used in the diesel version of the A518
contain
the
following
number of discs and plates:
•
transmission front/rear
clutch
has
4
discs and
5
steel plates
•
overdrive
clutch
has 5 discs and 6 steel plates
•
overdrive direct
clutch
has
8
discs
and
9
steel
plates
GOVERNOR
WEIGHT
ASSEMBLY
The governor weight assembly in the diesel A518
is
made of
alloyed
brass.
The diesel weight assembly
is
easily
identified
by the
distinctive
gold
color of the
alloyed
material.
The heavier weight assembly provides
the
shift
points
needed
to
offset lower operating
speeds
of
a
diesel engine.
The alloyed weight assembly is unique to the diesel
A518.
It is
not interchangeable
with
the weight
as-
semblies used in gas engine versions of the A518.
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