Leakage Inspection

External Sealing

External Sealing — 4R70W

Item	Part Number	Description
1	7902	Converter Assembly
2	7A248	Front Pump Seal Assembly
3	7A248	Front Pump Seal
4	N605789-S100	Bolt
5	7A106	Front Pump Body Assembly
6	7A136	Front Pump Gasket
7	390318-S100	Pipe Plug, 1/8-27 Dryseal Tapered (5 Req'd)
8	7005	Case Assembly
9	7034	Case Vent Assembly
10	7Z101	O-Ring Seal, 14.0 x 1.78 (2 Req'd)
11	7H103	Output Shaft Speed (OSS) Sensor
12	7052	Extension Housing Seal Assembly (Booted)
13	N803747-S1000	Bolt, M8-1.25 x 30 (6 Req'd)
14	7A039	Extension Assembly
15	7086	Extension Gasket
16	7B498	Manual Control Lever Seal Assembly
17	391139-S	O-Ring Seal, 0.864 x 0.070 (2 Req'd)
18	7Z276	Bulkhead Wiring Connector Assembly
19	7A194	Transmission Pan
20	7A191	Transmission Pan Gasket
21	7D273	Fluid Tube Connector Assembly (2 Req'd)
22	391346-S2	Converter Drain Plug, 1/8-27 Dryseal

Check the vehicle speed sensor (VSS) (9E731), output shaft speed sensor and the connector at transmission. Replace the rubber seal, if necessary.

NOTE: Fluid from other external sources can collect between the case (7005) and pan rail and give the appearance of a pan to case gasket leak. If fluid is present check the following positions as outlined.

Check for leakage at pan to case gasket.

Leakage at the pan to case gasket often can be stopped by tightening the retaining bolts to 12-15 Nm (9-11 lb-ft). Do not overtighten transmission pan bolts. If necessary, replace the pan to case gasket.

Check the fluid filler tube connection at the transmission case or transmission pan. If leakage is found here, install a new O-ring and press the fluid filler tube to the case. The filler tube bracket should align properly and be attached to the transmission or engine.

 CAUTION: Check the fluid lines and fittings between the transmission and the transmission fluid cooler (7A095) in the radiator tank for looseness, wear or damage. When fluid is found to be leaking between the case and the fluid cooler inlet tube or fluid cooler tube, tighten the fitting to 31 Nm (23 lb-ft).

Do not try to stop the fluid leak by increasing the torque beyond specification. This may cause damage to the case threads.

If the leak continues, replace the cooler line fitting and tighten to 20-26 Nm (15-19 lb-ft). The same procedure should be followed for fluid leaks between the transmission fluid cooler and cooler line fittings.

Check the engine coolant in the radiator (8005). If transmission fluid is present in the coolant, the transmission fluid cooler in the radiator is probably leaking.

The transmission fluid cooler can be further checked for leaks by disconnecting the fluid cooler tube and fluid cooler inlet tube from the cooler fittings and applying 345-517 kPa (50-75 psi) air pressure to the fittings. Remove the radiator cap (8100) to relieve the pressure buildup at the exterior of the fluid cooler tank. If the transmission fluid cooler is leaking and/or will not hold pressure, the transmission fluid cooler must be replaced. Refer to Section 07-02 for transmission fluid cooler replacement procedure.

If leakage is found at the wiring connector bulkhead assembly, replace the O-ring. Refer to Transmission in the Disassembly and Assembly portions of this section.

If leakage is found at the manual control lever (7A256), replace the manual control lever seal.

The transmission has five pipe plugs: four on the RH side of the case and one on the LH side. Inspect the plugs for leakage. Ensure they are tightened to 8-16 Nm (6-12 lb-ft). If tightening does not stop the leak, replace the plug.

When a converter drain plug leaks, remove the drain plug with a six-point wrench. Coat the threads with Pipe Sealant with Teflon® D8AZ-19554-A or equivalent meeting Ford specification ESG-M4G194-A and install plug. Tighten the drain plug to 28-30 Nm (21-23 lb-ft). Fluid leakage from the converter housing may also be caused by engine oil leaking past the rear main bearing seal, or from oil galley plugs. Verify the exact cause of the leak before starting service procedures.

Fluid Leakage in Torque Converter Area

When internal wear or damage has occurred in the transmission, metal particles, clutch plate material, or band material may have been carried into the torque converter (7902) and transmission fluid cooler. These contaminants are a major cause of recurring transmission troubles and MUST be removed from the system before the transmission is put back into service.

 CAUTION: Whenever a transmission has been disassembled to replace worn or damaged parts or because the main control valve body (7A100) sticks from foreign material, the main control valve body, transmission fluid cooler and fluid cooler inlet tube and fluid cooler tube MUST be cleaned and flushed by using the Rotunda Torque Converter/Oil Cooler Cleaner 014-00028 or equivalent. Under NO circumstances should an attempt be made to clean torque converter by hand agitation with solvent.

In diagnosing and correcting fluid leaks in the front pump support and gear (7A103) and torque converter area, use the following procedures to locate the exact cause of the leakage. Leakage at the front of transmission, as evidenced by fluid around the torque converter housing, may have several sources. By careful observation, it is possible, in many instances, to pinpoint the source of leak before removing the transmission from the vehicle. The paths which the fluid takes to reach the bottom of the torque converter housing are shown in the following illustration. The five steps following correspond with the numbers in the illustration.

Torque Converter Area Leak Points

1. Fluid leaking by the front pump seal lip will tend to move along the impeller hub and onto the back of the impeller housing. Except in the case of a total seal failure, fluid leakage by the lip of the seal will be deposited on the inside of the torque converter housing only, near the outside diameter of the housing.

2. Fluid leakage by the outside diameter of the front pump seal and front pump body will follow the same path that the leaks by the inside diameter of the front pump seal follow.

3. Fluid that leaks by a front pump-to-case bolt or pump gasket will be deposited on the inside of the torque converter housing only. Fluid will not be deposited on the back of the torque converter.

4. Fluid leakage from the converter drain plug, converter seal weld or converter-to-flywheel stud weld will appear at the outside diameter of the torque converter on the back face of the flywheel (6375), and in the converter housing only near the flywheel. Fluid leaks from the torque converter will leave a ring of fluid around the inside of the torque converter housing.

5. NOTE: White tissue paper may aid in determining the color (red is transmission fluid) and source of the leaking fluid.

   Engine oil leaks are sometimes improperly diagnosed as transmission pump gasket leaks. The following areas of possible leakage should also be checked to determine if engine oil leakage is causing the concern.

   1. Leakage at the valve cover gasket (6584) may allow oil to flow over the torque converter housing or seep down between the torque converter housing and cylinder block (6010), causing oil to be present in or at the bottom of the torque converter housing.
   2. Oil galley plug leaks will allow oil to flow down the rear face of the cylinder block to the bottom of the torque converter housing.
   3. Leakage at the crankshaft rear oil seal (6701) will work back to the flywheel, and then into the torque converter housing.
   4. Leakage at oil pressure sensor (9278).

Leak Check Test

The following procedures should be used to determine the cause of the leakage before service.

1. Remove the fluid level indicator (7A020) and note the color of the fluid. Original factory fill fluid is dyed red to aid in determining if leakage is from the engine or transmission. Unless a considerable amount of makeup fluid has been added or the fluid has been changed, the red color should assist in pinpointing the leak. However, a power steering leak may be mistaken for a transmission leak since both fluids are dyed red. Check the power steering system for leaks that could be misidentified as a transmission leak. Refer to Section 11-00.

2. Remove the torque converter housing cover. Clean off any fluid from the top and bottom of the torque converter housing, front of the case and rear face of the engine and oil pan (6675). Clean the torque converter area by washing with a suitable nonflammable solvent and blow dry with compressed air.

3. Wash out the torque converter housing, the front of the flywheel and the converter drain plugs. The torque converter housing may be washed out using cleaning solvent and a squirt-type oil can. Blow all washed areas dry with compressed air.

4. Start and run the engine until the transmission reaches its normal operating temperature. Observe the back of the cylinder block and top of the torque converter housing for evidence of fluid leakage. Raise the vehicle on a hoist and run the engine at fast idle, then at engine idle, occasionally shifting to the OVERDRIVE and REVERSE ranges to increase pressure within the transmission. Observe the front of the flywheel, back of the cylinder block (in as far as possible), and inside the torque converter housing and front of the case. Run the engine until fluid leakage is evident and the probable source of leakage can be determined.

Leak Check Test with Black Light

Oil soluble aniline or fluorescent dyes premixed at the rate of 2.5ml (1/2 teaspoon) of dye powder to 0.235L (0.5 pint) of transmission fluid have proved helpful in locating the source of fluid leakage. Such dyes may be used to determine whether an engine oil or transmission fluid leak is present, or if the fluid in the fluid cooler leaks into the engine coolant system. A black light must be used with the fluorescent dye solution.