Some owners of 2011-2014 Chevy Silverado 2500/3500 trucks equipped with the Allison A1000 automatic transmission may experience a bump feeling and/or a clunk noise when shifting from drive to reverse. Harsh shifting into reverse may be involved as well.
A revised calibration is available to address this concern. Update the transmission control module (TCM).
The calibration can be obtained by calling the tech line at (800) 828-6860.