FLUID LEAK OUT THE VENT NEW DESIGN VENT PIPE
Model and Year: 1988-90 C/K TRUCK WITH HM-117 MANUAL TRANSMISSION
BULLETIN COVERS: (Figure 2)
Some 1988 through 1990 C/K Trucks with an HM-117 manual transmission may develop a fluid leak out the vent connection at the transmission. This is caused when fluid leaks (seaps) past the joint between the vent pipe and the hose. The small amount of fluid that leaks (seaps) from this joint can be seen on the side of the transmission case, and a few drops may be found on the pavement under the vehicle after it has been parked for a while. The new design vent pipe (296) has a larger diameter on the hose end that will prevent fluid leaks.
IMPORTANT: When repairing a 1988 C/K Truck, also refer to Dealer Service Bulletin #88-44. However, even if the repairs described in that bulletin are performed, you must use the new design vent listed in this bulletin.
DATE OF PRODUCTION CHANGE: (Figure 1)
Starting January 17, 1990 (Julian Date 017), all 9CMY and 9KNY HM-117 transmissions were built with this new Vent Pipe (296).
SERVICE PROCEDURE: (Figures 2 & 3)
1) Remove transmission (also transfer case if applicable).
2) Remove existing vent pipe (296).
3) Install a new vent pipe (296).
- Lightly coat the ribbed end of the vent pipe with Loctite 609.
NOTICE: If excess loctite is used or if it is applied to the vent pipe hole rather than on the vent pipe ribbed end, the loctite may drip inside the transmission and onto the reverse shift rail. If this occurs, the transmission will not shift into reverse after the loctite cures.
- End of fitting towards clutch housing.
- Install with Tool J-38754.
4) Attach the rubber vent hose to the vent pipe and secure it with the worm clamp.
5) Reinstall the transmission (also transfer case if applicable).
SERVICE PARTS INFORMATION:
Part Number Description Transmission Models
15581915 Vent Pipe (296) 1988 CRY and KSY 1989-90 CMY and KNY
This part is currently available from GMSPO.
SERVICE NOTES:
Whenever an HM-117 transmission is serviced, use only the transmission fluid GM Part No.12345577 Lubricant 23 oz. container.
SERVICE MANUAL REFERENCE:
Refer to transmission replacement in the on-vehicle service section of the appropriate service manual for procedures.
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.
