This Preliminary Information communication provides information to the technician when the customer complaint on a noise from the transmission when the engine starts. The noise may be a clunk with a bump sensation. This condition may be caused by turning the engine off and then quickly restarting it. The transmission control module doesn?t have adequate time to power down and the 1-2-7-8-R along with the 1-2-3-4-5-R clutches will apply at maximum line pressure causing this concern. This is considered normal operation if the transmission control module is not allowed to power down before restarting the engine. The transmission control module needs the transmission to be placed in park the ignition turned off and the door opened and closed. After closing the door the transmission control module requires 2 minutes before the engine should be restarted. If the concern is present and duplicated after following the power down procedure the General Motors Technical Assistance Center for further direction.
