WARNING: This page is about a different car, the 2004 Ford Econoline, 2004 Ford E450 Super Duty, and 2004 Ford Cutaway. However, it is still accessible from the selected car via links, so may be relevant.
Remove the reverse clutch piston outer lip seal.
Fig 1: Removing Reverse Clutch Piston Outer Lip Seal
Courtesy of FORD MOTOR CO.
Remove the reverse clutch piston inner lip seal.
Fig 2: Removing Reverse Clutch Piston Inner Lip Seal