This bulletin applies to 2018-2019 Chevy Traverse and Equinox, 2019 Blazer, 2017-2019 Cruze and Malibu vehicles, all equipped with a GF9T 45/50/60/65 transmission. A “rotational click” noise may be heard after the engine is shut off.
The cause: The TCM is keeping the power-mode alive in Accessory for an extended period of time after engine shut off and the line pressure solenoid is staying in Dither Mode Control when there is no fluid pressure/pump causing the high side driver and solenoid body assembly buzz. The loudness and length of time may vary per vehicle.
This is a design characteristic and no repairs should be attempted. Chevy claims that there are no durability concerns.