1982 - 1993 Corvette: Service Bulletin: Buzzing Noise at Idle

Subject: BUZZING NOISE AT IDLE (INSTALL PRESSURE REGULATOR VALVE)
Model and Year:
1982-93 CAPRICE, CAMARO AND CORVETTE
1982-93 C/K, R/V, S/T, M/L AND G TRUCKS WITH 4L60 AUTOMATIC TRANSMISSION

Transmission Applications: 1982-1993 HYDRA-MATIC 4L60 (MD8)
Transmission Models: All
Vehicle Applications: B, D, F, Y - Cars C/K, R/V, S/T - Trucks G, M, L - Vans
Source: Chevrolet Service Bulletin
Bulletin Number: 93-29-7A

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 oll pressure instability at lower idle RPM.

CORRECTION:

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

SERVICE PARTS INFORMATION:

Description Part Number
----------- -----------
Valve, Pressure Regulator (III. 218) 8684048

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.