A/T - Proper Diagnosis of Oil Leaks
Number: 83-I-95Section: VIIc
Date: July, 1983
Subject: DIAGNOSING TRANSMISSION OIL LEAKS - THM 700-R4
TO: ALL CHEVROLET DEALERS
To diagnose a transmission oil leak properly, the following procedure should be used.
DIAGNOSIS PROCEDURE
The following procedure is performed on car.
1. Clean all residual oil from the transmission. (C.R.C.'s electramotive cleanser or equivalent is recommended.) Repeat cleaning process until all residual oil is removed.
2. Dust the entire transmission with a white powder (e.g. leak tracing powder or spray foot powder). If residual oil is left on the transmission, it will necessitate the cleaning and dusting procedure be repeated.
3. After normal operating temperature (170~F) has been obtained, let the transmission stand for at least thirty (30) minutes (engine off).
4. Inspect the transmission for leakage by following red oil traces left in the powder.
5. Once the leak has been diagnosed as to location and type (wetness, moist, damp, etc.), refer to the following repair procedure:
IMPORTANT: Steps 1-4 should be used when diagnosing any transmission for an oil leak.
6. Repeat Steps 1-4 following repair of suspect leak source.
POSSIBLE LEAK POINTS THM 700R4:
REPAIR PROCEDURE
Possible Leak Point
FIG. ITEM
NO. NO. PART NAME LEAK CAUSE CORRECTION
1 1 Transmission Oil Pan ^ Low Bolt Torque - Retorque & Recheck
^ Gasket Leak Bolts
POSSIBLE LEAK POINTS THM 700R4:
- Remove & Replace Gasket
1 2 Case ^ Porosity - Repair Per Service
Manual
^ Cracked - Replace Case
1 3 Cooler Fittings Or ^ Low Torque - Reseal & Retorque
Pressure Plugs
- Recheck
1 4 T.V. Cable Connector ^ Connector Cocked - Remove Connector &
and Interfering Reinstall
With Mount
- Remove & Replace
Seal Damaged Seal
^ Connector Cracked - Remove & Replace Cable
1 5 Servo Cover ^ Porosity - Replace (.See Fig 2)
FIGURE 2 Possible Leak Point:
2 1 ^ "O" Ring Damaged - Replace (See Fig 2)
2 2
POSSIBLE LEAK POINTS THM 700R4:
1 6 Fill Tube ^ Seal Missing or - Remove Fill Tube &
Damaged Replace Seal
^ Tube Bent Above - Replace Tube Transmission
POSSIBLE LEAK POINTS THM 700R4:
1 7 Converter Seal ^ Seal Damaged - Replace Seal
FIGURE 3 DRAINBACK PASSAGE:
3 - ^ Seal Blown out - (See Fig 3) Check
^ Seal Leak for Oversized Seal
(Not Damaged) Bore or Restricted
Drainback Passage
POSSIBLE LEAK POINTS THM 700R4:
1 8 Pump Assembly ^ Pump Bolts Loose - Retorque & Recheck
^ Pump to Case Ring - Remove & Replace
Cut or Damaged Ring (Recheck. If
Leak Persists Re-
place Oil Pump Body
With P/N 8642986)
or Repair (see Fig 3)
FIGURE 3 DRAINBACK PASSAGE:
3 - ^ Pump Porosity - Replace Pump Body
P/N 8642986
POSSIBLE LEAK POINTS THM 700R4:
REPAIR PROCEDURE
Possible Leak Point (Continued)
FIG. ITEM
NO. NO. PART NAME LEAK CAUSE CORRECTION
1 1 Converter Assembly ^ Hub or Seam Weld - Replace Converter
Leak
POSSIBLE LEAK POINTS THM 700R4:
1 10 Vent ^ Leaking - Check for Oil Over-
fill & Correct as
Necessary
1 11 Electrical Connector ^ " O" Ring Missing - Remove Connector
or Damaged and Replace Seal
^ Connector Missing - Remove & Replace or Damaged Conn.
POSSIBLE LEAK POINTS THM 700R4:
1 12 Manual Shaft ^ Seal Assembly - Remove & Replace
Damaged Seal
1 13 Governor Cover ^ Gaps in Sealant - Reseal (Loctite or
R.T.V.)
- Remove & Replace
1 14 Speedo Fitting ^ Low Bolt Torque - Retorque Bolt &
Recheck
^ Seal Damage - Remove & Replace
FIGURE 1 POSSIBLE LEAK POINTS THM 700R4:
1 15 Rear Extension ^ Porosity - Repair Per Service
^ Cracked Manual
^ Low Bolt Torque - Replace
^ Extension to Case - Retorque & Recheck
Seal Damaged - Replace
^ Extension Seal - Replace Assembly Torn or Damaged