Re: 94 Ford Taurus Wagon Overdrive issue (maybe?)
If you do a check with Google on Sable/Taurus transmissions you will find that it was a pretty bad design. Awful, really. Your 1994 is one of the worst years. My Sable was exactly the same. I'm sure that when you drained that trans fluid you found a lot of metal in it. It comes from failing clutches and other stuff that is destroying itself. Transmission shops are very familiar with the bad parts. You can keep on changing fluid and wondering about it but eventually you need to fix it. An Ammco shop rebuilt mine with all the newest parts as redesigned by Ford in the later '90's and my Sable is good to go. It is a big deal to R&R the transmission so don't bother with a junkyard replacement. Have yours made new or buy a crate trans. Mine cost a little under $2,000. Lot of money but far less than I've heard from some others. After Ford redesigned the clutches it is a very good transmission so don't give up on the car.
But don't waste time wondering what's wrong. One time it will just sit there when you rev it up!