TRANS OIL PAN LEAKS NEW PARTS AVAILABLE

Models Affected: All THM 200-4R Transmissions

Beginning in January 1984, all THM 200-4R transmissions are being produced using a new transmission oil pan (Figure 1), cork gasket and special hex bolts with conical washers (Figure 2). The new transmission oil pan has a continuous ribbed flange to reduce transmission oil leaks. When servicing any THM 200-4R transmission for transmission oil pan leaks, refer to the following procedure:

Service Procedure:

1. Diagnose source of leak to be certain leak is from the transmission oil pan area.

2. If a leak is determined to be from this area:

A. Remove the oil pan.

B. Clean the case oil pan face (with solvent) and visually inspect the case oil pan surface for damage and/or presence of R.T.V. sealant (room temperature vulcanizing sealant).

C. Make sure all R.T.V. sealant or other gasket material is removed from die case oil pan face.

3. Replace the past transmission oil pan, with service package number 8639907 which contains the following:

PART NUMBER QUANTITY DESCRIPTION ----------- -------- ----------- 8639556 1 Transmissim Oil Pan 8634198 1 Gasket Trans. Oil Pan 8643693 16 Bolt Asm, With Conical Washer

4. When replacing the oil pan, it is critical that a torque wrench is used to tighten the hex head screws. DO NOT USE IMPACT WRENCH! Torque all hex head screws to 11.0 N.m (9.0 ft lbs.), then retorque all the hex head screws a second time to the same specifications as above. The second re-torque is important because the gasket material relaxes after the first tightening.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.