A/T - Buzzing Noise at Idle

BULLETIN NUMBER:
93-7A-18

SECTION:
7A

NUMBER:
4

CORPORATE
REFERENCE NUMBER:
277142

DATE:
October 1992



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.