USE OF RTV SEALANT AS OIL PAN GASKET ON THM 125 TRANSMISSION

IN OCTOBER, 1980, A PRODUCTION TRIAL RUN WAS STARTED USING AN R.T.V. SILICONE BASE SEALANT IN PLACE OF THE CURRENT PRODUCTION LATEX COATED CORK OIL PAN GASKET. TO IMPROVE SEALING, A NEW DESIGN OIL PAN IS ASSEMBLED WITH THE R.T.V SEALANT. THE NEW DESIGN OIL PAN HAS THE SEALING BEADS REMOVED FROM THE PAN RAIL. SEE FIGURE 1.

SERVICE INFORMATION:

SUGGESTED OIL LEAK DIAGNOSIS PROCEDURE

1. CLEAN THE SUSPECTED AREA WITH SOLVENT TO REMOVE ALL TRACES OF OIL.

2. REMOVE THE CONVERTER SHIELD IF LEAK IS SUSPECTED AT ENGINE TRANSAXLE CONNECTION.

3. SPRAY SUSPECTED LEAK AREA WITH A WHITE POWDER TYPE SPRAY.

4. START ENGINE AND RUN AT HIGH IDLE.

5. REPAIR ANY LEAKS AND RECHECK AS NECESSARY.

OIL PAN REMOVAL AND REPLACEMENT

1. A SPECIAL BOLT WILL BE REQUIRED TO REMOVE ANY THM 125 OIL PAN ASSEMBLED WITH R.T.V. SEALANT. THIS SPECIAL BOLT CAN BE MADE FROM AN OIL PAN BOLT BY GRINDING DOWN A SECTION OF THE SHANK DIAMETER, JUST BELOW THE BOLT HEAD, TO APPROXIMATELY 3/16 INCH. SEE FIGURE 2.

2. DETERMINE IF THE TRANSMISSION OIL PAN WAS ASSEMBLED WITH A LATEX COATED CORK OIL PAN GASKET OR R.T.V. SEALANT.

IF A CORK IS NOT READILY VISIBLE BETWEEN THE OIL AN AND CASE OR IF THERE ARE NO SEALING BEADS IN THE PAN RAIL, THE OIL PAN WAS ASSEMBLED WITH THE R.T.V. SEALANT. IF THE R.T.V. SEALANT HAS BEEN USED, REMOVE THE OIL PAN USING THE FOLLOWING PROCEDURE.

A. REMOVE ALL THE OIL BOLTS EXCEPT THE TWO SHOWN IN FIGURE 3. REMOVE BOLT A (FIGURE 3) AND INSTALL THE SPECIAL BOLT, FINGER TIGHT, IN ITS PLACE. LOOSEN BOLT B ABOUT FOUR COMPLETE TURNS.

B. DO NOT TRY TO PRY THE OIL PAN LOOSE FROM THE CASE AS DAMAGE TO THE PAN RAIL OR CASE WILL RESULT.

C. USING A RUBBER MALLET, STRIKE THE OIL PAN CORNER INDICATED IN FIGURE 3, LIGHTLY IN EITHER DIRECTION, UNTIL THE SEAL BREAKS LOOSE. (CATCH THE FLUID IN A CONTAINER.)

D. REMOVE THE SPECIAL BOLT, TILT THE OIL PAN, AND ALLOW THE FLUID TO DRAIN.

3. TO REINSTALL THE OIL PAN, USE THE FOLLOWING PROCEDURE:

A. USING A SHARP EDGED PLASTIC SCRAPER, REMOVE ANY EXCESS OR LOOSE R.T.V. SEALANT REMAINING ON THE OIL PAN RAIL OR CASE. REMOVE ANY SEALANT THAT MAY HAVE FALLEN INTO THE OIL PAN. IF THE TRANSMISSION IS ON A REPAIR STAND, USE CARE NOT TO LET THE LOOSE SEALANT FALL INTO THE CASE WHILE SCRAPING.

B. USE A CLEAN DRY RAG AND SOLVENT TO DRY THE CASE FLANGE AND OIL PAN RAIL.

NOTICE: IF CASE FLANGE OR OIL PAN RAIL SURFACES ARE NOT DRY AND FREE OF OIL FILM LEAKAGE CAN RESULT.

C. APPLY A 1/16 INCH BEAD OF R.T.V. SEALANT TO THE OIL PAN RAIL (SEE FIGURE 1) AND REPLACE THE OIL PAN ON THE TRANSMISSION WHILE THE SEALANT IS WET.

D. INSTALL ALL OIL PAN BOLTS AND TORQUE TO 16 N.M (12 FT. LBS.). DO NOT USE THE SPECIAL BOLT FOR INSTALLATION OF THE OIL PAN. SAVE THIS SPECIAL BOLT AS A SERVICE TOOL.

NOTICE: DO NOT ATTEMP TO USE A LATEX COATED CORK OIL PAN GASKET WITH THE NEW DESIGN OIL PAN OR THE R.T.V. SEALANT WITH THE PAST DESIGN OIL PAN AS LEAKS CAN RESULT.

THE R.T.V. SEALANT CURRENTLY RECOMMENDED FOR SERVICE APPLICATIONS BY THE HYDRA-MATIC SERVICE DEPARTMENT CAN BE ORDERED FROM GMPD IN A THREE OUNCE TUBE, PART NUMBER 1052366, OR A TEN OUNCE CARTRIDGE, PART NUMBER 1052434.

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.