A/T - Buzzing Noise at Idle

Bulletin No.
T-93-21

File in Group
7

Number
246

Corp. Ref. No.
277142

Date
Nov. 1992



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.