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7-86
GROUP 7-AUTOMA TIC TRANSMISSION
or less of vacuum in
all
forward drive
ranges. The control pressure should
be
as shown
in
Fig. 7. Then move the
selector lever to
R.
With the vacuum
at 1
.
0 inch or less the control pres-
sure
should
be
as
shown in Fig. 7.
While making this pressure test, do
not hold the throttle open for more
than
the seconds in
each detent p•
sition. Between each
test
move the
selector lever to neutral and run the
engine at 1000 rpm for fifteen sec-
onds
to
cool the
converter.
If the Yacuum and pressure gauge
readings are within specifications, the
diaphragm
unit
and
transmission
control pressure regulating system
are operating properly.
If transmission control pressure
is
too low, too high. fails to increase
with
throttle
opening, or
is
extremely
erratic, use the procedure given under
the following appropriate heading to
resolve the
problem.
Control Pressure Not Within
Limits at 1.0 inches or Less
of Engine Vacuum (Test No.3)
If
idle
pressure
and
pressures at
10
inches of
vacuum
are
within
specifications but pressure at engine
stall
are
not within specification in
all ranges, excessive leakage, low
pump
capacity or
restricted oil pan
screen is
indicated.
If
stall
pressures are not within
specifications
for
specific ranges only,
CONTROL PRESSURE AT ZERO GOVERNOR RPM-
EnJineSpltd
Tllrottlt
Idle
Closed
,
As
Required
As
Required
As
Required
As
Required
this indicates excessive leakage in the
clutch or servo circuits used in those
ranges.
CONTROL PRESSURE IS
EXTREMELY ERRATIC
If transmission control pressure
is
extremely erratic in D and 2, check
the diaphragm unit tubes, hoses, and
diaphragm push rod as given under
Control Pressure Is High. If the vac-
uum source is satisfactory, check the
diaphragm unit and repeat the tests
for transmission control pressure. If
control pressure is still extremely
erratic, the trouble is in the transmis-
sion hydraulic regulating circuits.
Clean and inspect the control valve
body.
VACUUM DIAPHRAGM
ADJUSTMENT
The vacuum diaphragm fitted to
the F.M.X. transmission is adjust-
able. This diaphragm should not
be
interchanged with C4 or C6 trans-
missions.
The vacuum diaphragm assembly
has an adjusting screw in the vacuum
hose connecting tube (Fig. 8 ).
The inner end of the screw bears
against a plate which in turn bears
against the vacuum diaphragm spring.
All readings slightly high or all
readings slightly low may indicate
the vacuum unit needs adjustment to
Menlfokl
Yec.lnL H1o
llnp
Above 18<D
P, N, D, 2,1
R
10
D,
2.
1
at or
D. 2,1
Below 10
(at stall)
R
D1491-A
FIG. 8 - Adiustable
Vacuum Unit
correct a particular shift
condition.
For example,
if
the pressure at
10
inches of vacuum was 130 psi and
the pressure
at 1.0 inch of vacuum
was
190 psi, and upshifts and down-
shifts
were harsh, a diaphragm ad-
justment to reduce the diaphragm
assembly
spring force would
be
required.
If
the pressure readings are low,
an
adjustment to increase diaphragm
spring
force is required
.
To
increase control
pressure,
tur
the
adjusting screw in clockwise .T
reduce
control pressure, back the ac.
justing screw out by turning it coun-
terclockwise.
One complete turn of
the adjusting
screw (360 degrees) will
change
idle line control pressure ap-
proximately
2-3
psi
.
After the adjust-
ment is made, install the vacuum line
and
make all the pressure checks as
outlined
in
Figs.
7.
The diaphragm
should not
be
adjusted
to provide pressure
Control
Une Pressure (PSI)
56-82
59-111
82-112
146-175
184-221
fi >
At eltitudes ebove see level,
it
mey not be possible to obtein 18 inches of en&ine v1cuum •t idle. For
idle
vacuum of
less thin 18 inches,
refer to the followln& tlble to determine idle
speed
pressure speclflc•tion In D drlvin& r.n&e.
EnJint YICUUIII
Une Pressure
171nches
57-67
161nches
57-67
151nches
57-72
14 inches
57-79
13 Inches
57-86
12 inches
57-92
11 inches
57-99
FIG. 7
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