Advertisement
PART 7-3- F. M.X. AUTOMATIC TRANSMISSION
7-85
As the hose is removed from the
transmission vacuum unit, hold a fin-
ger over the end of the control rod.
When the hose is removed, the inter-
nal spring of the vacuum unit should
push the control rod outward
.
CONTROL PRESSURE TESTS-
The test results of the following
checks should agree with the specifi-
cations given in Fig. 7. When per ..
forming control pressure tests, make
certain that the service brake pedal
is held in the applied position. When
the transmission detent position of
D
is used, position the selector lever
at
D
on the quadrant.
:
'-"\'NG
~
I
!3~~---
-
~2"-.j -·
MANIFOLD
VACUUM
LINE HOSE
FIG.
4 -
Typical Vacuum Test
Line Connections
TEST NUMBER-I CONTROL
PRESSURE CHECK-AT
ENGINE IDLE
I. With the transmission in neu-
tral, and the engine at the correct
idle speed, the vacuum gauge should
show a mimimum of 18 inches. If the
vacuum reading is lower than 18
inches,
an engine problem is indi-
cated or there is leakage in the vac-
uum line
.
Make necessary repairs to
obtain a minimum vacuum reading of
18 inches
.
At different altitudes above sea
lev·
el,
it ma
y
not be possible to obtain
18 inches vacuum at engine idle
.
At
these altitudes, with idle vacuum of
less than 18 inches, refer to the speci-
fications in Fig. 7 to determine idle
speed control pressure in forward
driving ranges.
2. At engine idle, depress and re-
lease the accelerator ped<1l quickly
and observe the vacuum gauge
.
The
FIG. 5 - Vacuum Diaphragm
and Control Pressure Connecting
Point
amount of vacuum should decrease
and increase 'with the changes in
throttle openings
.
If the vacuum re-
sponse to changes in throttle open-
ing is too slow the vacuum line to
the diaphragm unit could be restrict-
ed. Make the necessary repairs be-
fore completing the test.
3. At engine idle, check the trans-
mission control pressure gauge at all
selector lever positions. Transmission
control pressures should agree with
the specifications shown in
Figs.
7).
FIG. 6 - Testing Transmission
Vacuum Unit for Leakage
Control Pressure is Low at
Engine Idle (Test No. 1)
If control pressure at engine idle
is low in all selector lever positions,
trouble other than the diaphragm
unit is indicated. When control pres-
sure at engine idle is low in all ranges,
check for excessive leakage in the
front oil pump, case, and control
valve body, or a sticking control pres-
sure regulator valve.
Control Pressure is High at
Engine Idle (Test No. 1)
If transmission control pressure at
engine idle is too high in all ranges,
the trouble may be in the diaphragm
unit or its connecting vacuum tubes
and hoses, throttle valve, or control
rod
.
With the engine idling, disconnect
lhe hose from the diaphragm unit
and check the engine manifold vac-
uum
.
Hold a thumb over the end of
the hose and check for vacuum. If
the engine speeds up when the hose
is disconnected and slows down as
the thumb is held against the end of
the hose, the vacuum source is satis-
factory
.
Stop the engine, and remove the
diaphragm unit and the diaphragm
unit control rod
.
Inspect the control
rod for
a
bent condition and for cor-
rosion. Check the diaphragm unit for
leakage with the distributor tester
(Fig.
6).
TEST NUMBER-2 CONTROL
PRESSURE CHECK AT 10
INCHES OF VACUUM
A control pressure check should be
made at 10 inches of vacuum in all
forward drive ranges.
Advance the throttle until the en-
gine vacuum reading is 10 inches and
check the control pressure regula-
tion. Control pressure should be as
shown in Figs. 7
Control Pressure Not Within
Limits at 1 0 inches of
Vacuum (Test No. 2)
If idle pressure is within specifica-
tions but
pressure.
at I 0 inches of
vacuum are not within specification
in all ranges, excessive leakage, low
pump capacity, or a restricted oil
pan screen is indicated
.
If pressures are not within specifi-
cations for specific selector lever po-
sitions only, this indicates excessive
leakage in the clutch or servo circuits
used in those ranges.
When the control pressure is with-
in specifications at engine idle, but
not within specifications at I 0 inches
of vacuum, the vacuum diaphragm
unit may need adjustment.
TEST NUMBER-3 CONTROL
PRESSURE CHECK AT
1.0 INCH OF VACUUM
Check control pressure at 1.0 inch
Advertisement
