A/T - 2-3 Upshift or 3-2 Downshift Clunk Noise
INFORMATIONBulletin No.: 01-07-30-042G
Date: September 22, 2011
Subject: Information on 2-3 Upshift or 3-2 Downshift Clunk Noise
Models:
2012 and Prior GM Passenger Cars and Light Duty Trucks
Equipped with 4L60-E, 4L65-E or 4L70-E Automatic Transmission (RPOs M30, M32, M70)
Supercede:
This bulletin is being revised to add model years. Please discard Corporate Bulletin Number 01-07-30-042F (Section 07 - Transmission/Transaxle).
Important
For 2005 model year fullsize utilities and pickups, refer to Corporate Bulletin Number 05-07-30-012.
Some vehicles may exhibit a clunk noise that can be heard on a 2-3 upshift or a 3-2 downshift.
During a 2-3 upshift, the 2-4 band is released and the 3-4 clutch is applied. The timing of this shift can cause a momentary torque reversal of the output shaft that results in a clunk noise. This same torque reversal can also occur on a 3-2 downshift when the 3-4 clutch is released and the 2-4 band applied. This condition may be worse on a 4-wheel drive vehicle due to the additional tolerances in the transfer case.
This is a normal condition. No repairs should be attempted.
Disclaimer