Chevrolet 30 Series 1967 Service Manual page 436

CLUTCHES AND TRANSMISSIONS 7-50
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the source of the leak can be deceiving due to "wind
flow" around the engine and transmission.
The suspected area should be wiped clean of all oil
before inspecting for the source of the leak. Red dye is
used in the transmission oil at the assembly plant and
will indicate if the oil leak is from the transmission.
The use of a "black light"* to identify the oil at the
source of leak is also helpful. Comparing the oil from
the leak to that on the engine or transmission dip stick
(when viewed by black light) will determine the source of
the leak.
Oil leaks around the engine and transmission are gen­
erally carried toward the rear of the car by the air
stream . For example, a transmission "oil filler tube
to case leak" will sometimes appear as a leak at the rear
of the transmission. In determining the source of an oil
leak it is most helpful to keep the engine running.
POSSIBLE POINTS OF OIL LEAKS
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. REAR EXTENSION LEAK
a. Attaching bolts not correctly torqued.
b. Rear seal assembly - damaged or improperly
installed.
c. Gasket seal - (extension to case) damaged or im­
properly installed.
d. Porous casting.
3. CASE LEAK
a. F iller pipe "O" ring seal damaged or missing;
misposition of filler pipe bracket to engine -
"loading" one side of "O" ring.
b. Modulator assembly "O" ring seal - damaged or
improperly installed.
c. Governor cover, gasket and bolts - damaged,
loose; case face leak.
d. Speedo gear - "O" ring damaged.
e. Manual shaft
installed.
f. Line pressure tap plug - stripped, shy sealer
compound.
g. Parking pawl shaft cup plug - damaged, improp­
erly installed.
h. Vent pipe (refer to Item 5).
i. Porous case.
4. FRONT END LEAK
a. Front seal - damaged (check converter pack for
nicks, etc., also for pump bushing moved for­
ward); garter spring missing from pump to con­
verter seal.
b. Pump attaching bolts and seals - damaged, m iss­
ing, bolts loose.
c. Converter - leak in weld.
d. Pump "O" ring seal - damaged.
pump groove and case bore).
e. Porous casting (pump or case).
5. OIL COMES OUT VENT PIPE
a. Transmission over-filled.
b. Water in oil.
c. Pump to case gasket mispositioned.
*A "Black Light" testing unit may be obtained from several different service tool suppliers.
seal - damaged, improperly
(Also check
d. Foreign material between pump and case, or be­
tween pump cover and body.
e. Case - porous, pump face improperly machined.
f. Pump - shy of stock on mounting faces, porous
casting.
C A Si POROSITY—REPAIR
Transmission leaks caused by aluminum case porosity
have been successfully repaired with the transmission in
the vehicle by using the following procedure.
1. Road test and bring the transmission to operating
temperature.
2. Raise the car and, with the engine running, locate the
source of the oil leak. Check for leaks in all operat­
ing leaks.
NOTE: The use of a m irror will be helpful in
finding leaks.
3. Shut off engine and thoroughly clean area with a sol­
vent and air dry.
4. Using the instruction of the manufacturer, mix a
sufficient amount of epoxy cement, part #1360016, to
make the repair.
5. While the transmission is still hot, apply the epoxy
to the area, making certain that the area is fully
covered.
. Allow epoxy cement to dry for three hours and re­
6
test for leaks, as outlined in Steps 1 and 2.
OH. PRESSURE CHECK
With Vehicle Stationary
Transmission oil pressure gauge and engine tachom­
eter should be connected and the oil pressures should
check as follows:
1. Pressures indicated below are at 0 output speed with
the vacuum modulator tube disconnected and with
engine at rpm.
1 2 0 0
Approximate
Altitude of Check
(Ft. above seal level)
0
2 , 0 0 0
4,000
6 , 0 0 0
8 , 0 0 0
1 0 , 0 0 0
1 2 , 0 0 0
14,000
2. Pressures indicated below are with the vacuum tube
connected for normal modulator operation, and with
the engine at rpm.
1 2 0 0
NOTE: Pressures are not significantly af­
fected by altitude or barometric pressure when
the vacuum tube is connected.
Drive, Neutral, Park
70
Drive L l
Neutral or
Park L2 Reverse
150 150 244
150 150 233
145 150
2 2 2
138 150
2 1 2
132
150 203
126 150 194
150 186
1 2 1
116 178
150
L l or L2 Reverse
150 107
CHEVROLET TRUCK SERVICE MANUAL