A/T - Gear Whine Noise
File In Section: 7 - TransmissionBulletin No.: 47-71-31
Date: October, 1994
Subject:
Transaxle Gear Whine Noise Between 20-40 MPH
(Replace Final Drive and Update PCM Calibration)
Models:
1994 Buick Skylark
1994 Chevrolet Beretta, Corsica
1994 Oldsmobile Achieva
1994 Pontiac Grand Am
Transaxle Applications:
Hydra-Matic 4T60-E (RPO M13)
Transaxle Models:
4CLW, 4PHW, 4WBW, 4WSW
Condition (Figure 1)
Some owners of the listed vehicles equipped with a Hydra-Matic 4T60-E transaxle may experience a final drive gear whine noise. The final drive noise may be detected during a light acceleration or closed throttle deceleration between 20 and 40 MPH.
Cause
This condition may be due to a combination of the final drive gear tooth design and vehicle powertrain mounting.
Correction
New final drive assemblies with a fine pitch tooth design are now available to repair this condition. A 3.05 ratio fine pitch final drive replaces the 3.06 ratio final drive and a 3.29 ratio fine pitch final drive replaces the 3.33 ratio final drive. Because of the different ratios of the new final drive assemblies, it is also necessary to install a revised PCM PROM calibration. All 1994 production and SRTA models continue to use the current design final drive assemblies.
Service Information
Drive the vehicle and confirm the following:
^ The noise is only present during a light acceleration or closed throttle deceleration between 20 and 40 MPH.
^ The noise is not present in PARK or NEUTRAL ranges.
^ The noise is present in 2nd, 3rd or 4th gear (does not go away in 3rd gear).
If all of the above conditions are met, the final drive assembly should be replaced and the PCM calibration MUST be updated.
Parts Information
The final drive assembly should be replaced with the appropriate part numbers listed as follows:
Parts are currently available from GMSPO.
MEMCAL part numbers for 2.3L (RPO L40 or LD2) applications are as follows:
Parts are currently available from GMSPO.
The new "Flash" PROM for 3.1L (RPO L82) applications will be available on the September, 1994 CD released by STG. Part numbers are as follows:
Warranty Information
For vehicles repaired under warranty, use: