WARNING: This page is about a different car, the 2003 Mercury Marauder, 2003 Mercury Grand Marquis, and 2003 Ford Crown Victoria. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Exploded View Of Clutch - Reverse
Courtesy of FORD MOTOR CO.
The reverse clutch couples the input shaft to the reverse sun gear, applied in reverse range only.