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TURBO HYDRA-MATIC 250 TRANSMISSION
7A2-3
Possible Points of Fluid Leak
1. Transmission Oil Pan Leak:
a. Attaching bolts not correctly torqued.
b. Improperly installed or damaged pan gasket.
c. Oil pan gasket mounting face not flat.
2. Extension Housing:
a. Attaching bolts not correctly torqued.
b. Rear seal assembly damaged or improperly installed.
c. Square seal, extension to case, damaged or improperly
installed.
d. Governor cover not tight, gasket damaged or leak
between case face and gasket.
e. Speedometer gear "0" ring damaged.
f. Manual shaft seal damaged or improperly installed.
g. Line pressure tag plug loose.
h. Vent pipe (refer to item 5).
i. Porous casting.
4. Leak at Front of Transmission:
a. Front pump seal leaks
1. Seal lip cut. Check governor hub, etc.
2. Bushing moved and damaged. Fluid return hole
plugged.
3. No fluid return hole.
b. Front pump attaching bolts loose or bolt washer type
seals damaged or missing.
c. Front pump housing "0" ring damaged or cut.
d. Converter leak in weld area.
e. Porous casting (pump).
5. Fluid Comes Out Vent Pipe:
a. Transmission over-filled.
b. Water in fluid.
c. Foreign material between pump and case or between
pump cover and body.
d. Case
-
porous near converter bosses. Front pump
cover or housing oil channels shy or stock near breather.
e. Pump to case gasket mis-positioned.
FLUID PRESSURE CHECK
While vehicle is stationary (parking brake on), engine
speed set to 1200 rpm, transmission oil pressure gage attached
to line pressure tap (Fig. 7A2-2) and vacuum modulator tube
disconnected, transmission line pressure should read 120 psi
in Drive, 120 psi in L1 or L2 and 245 psi in Reverse.
While vehicle is stationary (parking brake on), engine
speed set to maintain 16 inches hg absolute mainfold pressure,
transmission oil pressure gage attached, and vacuum
modulator tube connected, the transmission line should read:
55 psi
-
Drive, 82 psi
-
L1-L2, 88 psi
-
Rev. (Fig. 7A2-3).
CASE POROSITY REPAIR
External fluid leaks caused by case porosity can be
successfully repaired with the transmission in the vehicle by
using the following recommended procedures:
1. Road test and bring the transmission to operating
temperature, approximately 180 degrees
F.
2. Raise vehicle on a hoist or jack stand, engine running,
and locate source of fluid leak. Check for fluid leaks in Low,
Drive and Reverse.
Fig. 7A2-2
Pressure
Tap
Location
3. Shut engine off and thoroughly clean area to be
repaired with a suitable cleaning solvent and a brush
-
air dry.
A clean, dry soldering acid brush can be used to clean
the area and also to apply the epoxy cement.
4. Using instructions of the manufacturer, mix a
sufficient amount of epoxy to make the repair. Make certain
the area to be repaired is fully covered.
5. Allow cement to cure for .3 hours before starting
engine.
6. Road test and check for leaks.
ALTITUDE OF
4348
Fig.
7A2-3 Oil
Pressure Check-Vacuum Modulator
Connected
V A C U U M MODULATOR DIAGNOSIS
A defective vacuum modulator can cause one or more
of the following complaints:
1. Harsh upshifts and downshifts.
2. Delayed upshifts.
3. Soft upshifts and downshifts.
4. Slips in low, drive and reverse.
5. Transmission overheating.
6. Engine burning transmission fluid.
If any one of the above complaints are encountered, the
modulator must be checked.
Vacuum Diaphragm Leak Check
Insert a pipe cleaner into vacuum connector pipe as far
as possible and check for the presence of transmission fluid.
If fluid is found, replace modulator.
Gasoline or water vapor may settle in vacuum side of
the modulator. If this is found without presence of fluid,
modulator is serviceable and should not be changed.
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