TSB 93-7-5: A/T - Buzzing Noise at Idle

Details

Bulletin Number: 93-7-5 Reference Number: 277142 Publish Date:10/92 Subject: BUZZING NOISE AT IDLE (INSTALL NEW PRESSURE REGULATOR VALVE) Models Affected: 1984-1993 FIREBIRD MODELS W/4L60 TRANSMISSION TRANSMISSION APPLICATIONS: 1984-1993 HYDRA-MATIC 4L60 (MD8) TRANSMISSION TYPE 4L60 700R4 TRANSMISSION MODELS: All CONDITION: Some 1984-1993 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 (Ill. 218) has been made which will improve the oil pressure stability at lower RPM. SERVICE PARTS INFORMATION: Description Part Number Valve, Pressure Regulator (Ill. 218) 8684048 Parts are currently available from GMSPO. WARRANTY INFORMATION: Labor Operation No.: K6550 Labor Time: Use Applicable Labor Time.