One problem related to transmission pump has been reported for the 1999 Ford Windstar. The most recently reported issues are listed below.
I lost all acceleration while in the outside lane on the interstate. Fortunately I was able to coast to the emergency parking lane without incident, however, without the ability to accelerate (no gears at all) it could have been quite dangerous on a busier stretch of highway. I was towed to the nearest Ford dealer and had to replace the transmission pump, shaft, valve body and seals.