A/T - Second Gear Vibration

Group Ref.: Transmission

Bulletin No.: 377138A

Date: December, 1993

SUBJECT:
SECOND GEAR VIBRATION AT 3000-5000 RPM (INSTALL SHAFT PACKAGE)

MODELS:
1991-93 BUICK LE SABRE, PARK AVENUE, REGAL AND RIVIERA
1991-93 CADILLAC DEVILLE, ELDORADO, FLEETWOOD AND SEVILLE
1991-93 CHEVROLET LUMINA
1991-93 OLDSMOBILE CUTLASS SUPREME, EIGHTY EIGHT, NINETY EIGHT AND TORONADO
1991-93 PONTIAC BONNEVILLE AND GRAND PRIX
1992-93 CHEVROLET LUMINA APV
1992-93 OLDSMOBILE SILHOUETTE
1992-93 PONTIAC TRANS SPORT

TRANSAXLE APPLICATIONS:
1993 HYDRA-MATIC 4T60-E (RPO M13)

This bulletin is being revised to correct the artwork.





CONDITION: (Figure 1)

Some vehicles may exhibit a transaxle vibration at an engine speed between 3000-5000 RPM when in second gear (only).

NOTE:
Second gear vibration sounds very similar to grounded out engine mounts.

CAUSE:

When engine speed is between 3000-5000 RPM, a disturbance may occur between the output shaft assembly near the bearing, input sun gear (511) and components attached to the sun gear shaft (668). This disturbance may be enough to cause a vibration while in second gear.





CORRECTION: (Figure 2)

The Input Sun Gear Bearing (511) and Input Sun Gear Bearing Journal have been removed from the output shaft (510), and replaced with a (new) 4th clutch shaft to input housing bearing (723). The 4th clutch shaft to input housing bearing is located on the (inner diameter) Input Shaft of the Input and 3rd Assembly. To accommodate this new 4th clutch shaft to input housing bearing (723), a bushing has been added to the base (outer diameter) of the Shaft Assembly 4th Clutch, (504).

NOTE:
Input Sun Gear (668) was also modified. The surface finish specification has been reduced from the inner diameter (input Sun Gear Bearing surface) making it unable to be used in a transaxle with a Input Sun Gear Bearing (511). The prior Input Sun Gear (Part Number 8682441) can be used in either application. The removal and/or relocation of the above bearings isolated the offending components and dampened the vibration while in 2nd gear.

DATE OF PRODUCTION:
Effective June 1, 1993 (Julian Date 152) all 1993 HYDRA-MATIC 4T60-E transaxles will be built with the new 4th clutch shaft to input housing bearing and new Hub and Shaft Assembly 4th Clutch. HYDRA-MATIC 4T60 transaxles will be unaffected. No HYDRA-MATIC 4T60 production or SRTA transaxles will be built with the new 4th clutch shaft to input housing bearing and new Shaft Assembly 4th Clutch.

SRTA INFORMATION:
The 4T60-E Service Replacement Transmission Assembly (SRTA) will phase the 4th Clutch Shaft to Input Housing Bearing and Hub and Shaft Assembly 4th Clutch into production when sufficient parts are available. SRTA transaxles are scheduled to be available after November 15, 1993.

Parts are expected to be available on November 15, 1993.

WARRANTY INFORMATION:

For vehicles repaired under warranty use:

Labor Operation Number: K7537