For 1990-2009 cars

# BUZZING NOISE AT IDLE (INSTALL PRESSURE REGULATOR VALVE)

#### SUBJECT: BUZZING NOISE AT IDLE (INSTALL NEW PRESSURE REGULATOR VALVE)

VEHICLES AFFECTED: 1982-93 "B,D,F,Y" MODELS, "C/K, R/V, SIT" TRUCKS AND "G,M,L" VAN WITH 4L60 TRANSMISSION

#### CONDITION:

Some 1982-1993 vehicles equipped with a HYDRA-MATIC 4L60 transmission may have a buzzing noise coming from the transmission when the vehicle is at idle. The buzzing noise may be noticed more when the vehicle is in reverse at idle.

#### CAUSE:

The buzzing noise may be a result of pressure regulator valve oscillating due to oil pressure instability at lower idle RPM.

#### CORRECTION:

A new pressure regulator valve (Illustration # 218) has been made which will improve the oil pressure stability at lower RPM.

SERVICE PARTS INFORMATION:

Description Part Number Valve, Pressure Regulator 8684048 (Illustration # 218)

For vehicles repaired under warranty use: Labour Operation: K6550 Valve, Pressure Regulator--R&R or Replace

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.