BUZZING NOISE AT IDLE (INSTALL PRESSURE REGULATOR VALVE). GMC Truck S15 Pickup - 2WD 1990

For 1990-2009 cars

# BUZZING NOISE AT IDLE (INSTALL PRESSURE REGULATOR VALVE)

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

#### MODELS: 1982-93 C/K, R/V, S/T TRUCKS AND G/M/L VANS WITH 4L60 TRANSMISSIONS

#### CONDITION:

--------- Some 1982-93 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 (See Figure 1) has been made which will improve the oil pressure stability at lower RPM.

#### SERVICE PARTS INFORMATION:

Part Description Number ----------- ------- Valve, Pressure Regulator (See Figure 1) 8684048

Parts are expected to be available on October 5, 1992. In case of limited inventory, parts will be placed on 400 control to waive VIP surcharges. Only verifiable emergency VIP orders will be accepted. GMSPO will make every effort to obtain parts. However, the part will be shipped premium transportation at dealer's expense and all other order types will be placed on back order until the 400 control is removed.

#### WARRANTY INFORMATION:

Labor Operation: K6550 Valve, Pressure Regulator - R&R or Replace

Use the appropriate labor time in the labor time guide.

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.