WARNING: This page is about a different car, the 2006 Mercury Grand Marquis and 2006 Ford Crown Victoria. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Identifying Transmission Code
Courtesy of FORD MOTOR CO.
The transmission codes are:
Q - 4-speed automatic overdrive, (4R75E) Livonia
S - 4-speed automatic overdrive, (4R75E) Sharonville