'BUZZ' CONDITION 2004R TRANSMISSION
NEW DESIGN PUMP ASSEMBLY TO ELIMINATE A "BUZZ" CONDITION - 1981-1982 THM 200-4R
New design pump assemblies were released for the THM 200-4R late in the 1982 model year. This new design eliminates a buzz condition that is caused by the pressure regulator valve. The design changes involve a new pump body, pump cover, and pressure regulator valve with orifice.
When servicing the pump body assembly or cover assembly on all 1981 and 1982 THM 200-4R transmissions, a complete pump assembly must be ordered (see chart below).
MODEL TRANSMISSION PUMP ASSEMBLY YEAR MODEL NUMBER
1981-1982 BY 8639077 1982 AA,AP 8639077 1982 OM 8639135 1982 AH 8639079
MODEL TRANSMISSION PRESSURE REGULATOR YEAR MODEL NUMBER
1981 & 1982 All Models 8637546
SERVICE INFORMATION
1. Follow proper Service Manual procedures for removal and installation of pump assemblies.
2. The solenoid and filter assembly must be removed before pulling the pump assembly from the case. Failure to follow this procedure can damage the solenoid, filter or "O" rings.
3. DO NOT MIX the old pump halves (body and cover) with the new design pump halves as this may create a "no drive" condition or may not eliminate the "buzz" condition.
4. New design pressure regulator valve listed above can be used with either new or previous design pump cover and body assemblies.
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.
