A/T - Diagnosing Oil Leaks
Bulletin No. T 83-51File In Group 7
Number 63
Date Mar. '83
DIAGNOSING OIL LEAKS ON 125C, 200C, 325-4L, AND 200-4R TRANSMISSIONS
When any THM transmission oil leak is detected, it is very important that they are diagnosed properly, as to the location and type of leak.
The following procedure will help in diagnosing the type and location of the leak and will suggest a correction method.
DIAGNOSIS PROCEDURE: (All Models)
The following procedure can be performed on car.
1. Clean all residual oil from the transmission, concentrating on the transmission oil pan to case mating areas (all models), TV cable connector (all models), transmission oil pan to sprocket cover interface area (325-4L model), final drive to case connection (325-4L model), and valve body cover to transmission oil pan interface area (125C model) (CRC's electramotive cleaner, or equivalent is recommended).
2. Dust the entire transmission with a white powder (e.g., Leak Tracing Powder or Foot Powder, Spray).
3. After normal operating temperature (170~F) has been obtained, let the transmission stand for at least (30) thirty minutes.
4. Inspect the transmission for leakage by following red oil traces left in the powder. (If residual oil is left on the transmission oil pan or sprocket cover, it will be necessary for the cleaning and dusting procedure to be repeated.)
5. Once the leak has been diagnosed as to location and type (wetness, moist, damp, etc.), refer to the following repair procedure:
FIGURE 1 - Diagnosing Oil Leaks on THM 325 4L:
FIGURE 2 - Diagnosing Oil Leaks on THM 200 4R:
FIGURE 3 - Diagnosing Oil Leaks On THM 200C:
FIGURE 4 - Diagnosing Oil Leaks On THM 125C:
REPAIR PROCEDURE:
ALL MODELS (FIGURE 1, 2, 3, AND 4)
ITEM PART NAME LEAK CAUSE CORRECTION
2 Transmission Oil Pan Low Bolt Torque Retorque and Recheck Bolts
Gasket Leak Remove and Replace Gasket
Broken RTV Bead Remove Cover and Reseal with
RTV
3 TV Cable Connector Cocked Remove Connector and Reinstall
Connector "C" and interferring with
mount
Seal Damaged Remove and Replace Seal
ITEM PART NAME LEAK CAUSE CORRECTION
Connector Cracked Remove and Replace Cable
Fill Tube "D" Seal Missing or Damaged Remove Fill Tube and Replace
Seal
Electrical "O" Ring Missing or Remove Connector and Replace
Connector "E" Damaged Seal
Connector Missing or Remove and Replace Connector
Damaged
4 Manual Shaft Seal Assembly Damaged Remove and Replace Seal
5 Governor Cover "O" Ring Damaged Remove and Replace "O" Ring
Low Bolt Torque Retorque Bolts and Recheck
6 Speedo Fitting Low Bolt Torque Retorque Bolt and Recheck
Seal Damaged Remove and Replace Seal
7 Servo Cover "O" Ring Damaged Remove and Replace "O" Ring
8 Cooler Fittings Low Fitting Torque Retorque Fitting and Recheck
Cracked Fitting Replace and Retorque Fitting
11 Converter Assembly Hub or Seam Weld Leak Remove and Replace Converter
12 Converter Seal Seal Damaged Remove and Replace Seal
13 Vent Leaking Check for the following and
correct as necessary:
A. Oil Overfill
B. Blocked Drainback holes in sprocket support
C. Engine Coolant in oil
FIGURE 1 - Diagnosing Oil Leaks on THM 325 4L:
325-4L ONLY (FIGURE #1)
ITEM PART NAME LEAK CAUSE CORRECTION
1 Sprocket Cover RTV Bead Broken Remove Cover and Reseal with
RTV
Cracked Cover Replace Cover
ITEM PART NAME LEAK CAUSE CORRECTION
Corner "A" Leak Past Design Case-Drill through
and Add Nut, Bolt and Lock Washer
Corner "B" Leak Remove Cover and Reseal with
RTV
9 Case Face to Low Bolt Torque Retorque Bolts and Recheck
Final Drive
10 Case Face to Plug Loose Remove Plug and Replace
Final Drive (Leaking) (Loctite Plug)
Governor Cover
Plug High Drive Plug into Case Below Face
Surface
FIGURE 2 - Diagnosing Oil Leaks on THM 200 4R:
FIGURE 3 - Diagnosing Oil Leaks On THM 200C:
200C AND 200-4R ONLY (FIGURES 2 AND 3)
ITEM PART NAME LEAK CAUSE CORRECTION
14 Pump Assembly Pump Bolts Loose Retorque Bolts and Recheck
Pump "O" Ring Cut Remove "O" Ring and Replace
or Damaged
Pump Porosity Replace Pump
15 Rear Extension Torn or Damaged Remove Seal and Replace
Seal
FIGURE 4 - Diagnosing Oil Leaks On THM 125C:
125C ONLY (FIGURE 4)
ITEM PART NAME LEAK CAUSE CORRECTION
16 Valve Body Cover Low Bolt Torque Retorque Bolt and Recheck
to Case Assembly
RTV Bead Broken Remove Cover and Reseal with
RTV Gasket
Gasket Leak Remove Gasket and Replace
17 Axle Shaft Seals Seals Damaged Remove Seals and Replace