You may want to watch this..
This is the Cheapest & Best alternative to fill the transmission-http://www.amazon.com/gp/product/B000BQW5LK/ref=as_li_tl?ie=UTF8&camp=1789&creative=390957&c...
www.youtube.com
Could be the culprit.. Cheap fix if it is.
My 2010 Mountaineer had a similar issue to what you experienced and this was the cause.
I have done this repair on my back on the garage floor with the Navigator on jack stands. It's not difficult, just time consuming. And unfortunately the pan gasket was not reusable in my case as there was a large nick out of the rubber part, so I had to stop and go to the Ford dealer to get another one. I also stopped while I was out and bought some wobble extensions at Harbor Freight and that made getting the pan bolts back on a lot easier.
I also acquired an inch-pounds torque wrench before I started. You could probably just put them on "snug" by feel but I felt better using the Ford spec torque. And it doesn't leak using the torque spec, which is probably the most important thing.
Other parts used: new Motorcraft transmission filter, the plastic sleeve, and Lubeguard transmission assembly lube to make the filter stick in place as you're putting the pan back on.
Note: if you get a solid check engine light that comes on after plugging the PCM connector back up and putting the battery terminal back on, don't automatically assume it's wrong. After removing battery power the check engine light will come on for 8 seconds to indicate the system is not ready. I fussed over this for a couple of extra hours, but as it turned out everything was OK and the connector was attached appropriately.