When you do a pan drop and screen filter service on a 4T45E tranny, it is not recommended to just drain the fluid and dump in an arbitrary amount of ATF (Dextron-III) into it. The proper way is to check ATF level via an inspection hole located on the side of the passenger side of the transaxle. It's adjacent to the engine oil drain plug. ATF is added until the fluid drips out of the inspection hole. Otherwise you may find yourself under or overfilled.
It's the same for a Malibu and Grand Am or any GM car with a 4T45E transmission.