Low Fluid Level
WARNING: This page is about a different car, the 2005 Ford RV Cutaway, 2005 Ford Econoline, and 2005 Ford Cutaway. However, it is still accessible from the selected car via links, so may be relevant.
A low fluid level could result in poor transmission engagement, slipping, or failure. This could also indicate a leak in one of the transmission seals or gaskets.