For 1990-2009 cars

# BUZZING NOISE AT IDLE (INSTALL PRESSURE REGULATOR VALVE)

#### SUBJECT: BUZZING NOISE FROM THE TRANSMISSION AT IDLE

#### MODELS AFFECTED: 1990-1992 BROUGHAMS 1993 FLEETWOODS WITH HYDRA-MATIC 4L60

Some 1990-1992 Broughams and 1993 Fleetwoods equipped with a Hydra-Matic 4L60 transmission may experience 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.

This buzzing noise may be a caused by the pressure regulator valve oscillating due to oil pressure instability at lower idle rpm.

To correct this condition replace the pressure regulator valve (refer to Figure 1) with P/N 8684048. This new pressure regulator valve will improve the oil pressure stability at lower rpm.

Parts are currently available from GMSPO.

For warranty purposes use Labor Operation K6550 at .9 hour for 1990 - 1992 Broughams and .8 hour for 1993 Fleetwoods.

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.