A/T - Drive Line Vibration/Gear Rattle With TCC Applied

NUMBER: 93-T-17

CORP.REF.NO: 277145

DATE: November 1992

SECTION: 7, 4L60 & 4L60-E

SUBJECT:
DRIVELINE VIBRATION AND/OR GEAR RATTLE WITH TCC APPLIED - INSTALL NEW TORQUE CONVERTER ASSEMBLY

MODELS/YEARS:
1992-93 BRAVADA

CONDITION:
Some 1992-93 Bravadas equipped with 4.3 liter (L35) engine and the HYDRA-MATIC 4L60 or 4L60-E transmission built before Julian Date 223 (August 10, 1992) may exhibit a rattle or driveline vibration with the torque converter clutch (TCC) applied at low engine speeds (1000-2000 RPM).

CAUSE:
The rattle or driveline vibration may be due to the stiffness of the spring rate of the damper springs in the torque converter.

CORRECTION:
Install a new torque converter assembly which improves the rattle in the 1000-2000 RPM operating range.

Diagnostic Information:

The rattle or driveline vibration condition only occurs in fourth gear with TCC applied. Use the following procedure to determine if the vehicle has this condition:

1. Accelerate the vehicle to achieve fourth gear and confirm that TCC is applied.

2. Maintain low engine speed (1000-2000 RPM) then crowd the throttle to above 25 percent TPS to induce the rattle or driveline vibration.

Note:
Excessive throttle input will disengage the TCC. Applying the brake will also disengage the TCC.