Check the fluid like stated and if it low fix your leak, fill, and clear code. If fluid is at normal level than you might overfill it half inch above the cross hatched area to eliminate a filter problem. Is the pan bent.. ??
If it is not low on fluid or pan bent (damages the filter usually) than you more than likely have an P01811 slip code from a bad internal seal.
Son' father-in-law gave his 2000 Taurus to him when their 95 Escort blew the engine about six years, just married and broke. Said he would have to spend a couple of thousand on it to replace the rear transmission seal. But add a quart every 800 miles or so.
I just dropped in that Lucas AT seal condition for around eight bucks, 100K miles later, still hasn't leaked a drop. Is this luck? A couple of weeks ago, his engine was tripping over its own feet, CEL was flashing, engine was stalling. Told him to put in a full can of Seafoam in a half a tank of gas and drive it. In four days, purring like a kitten again. Is this more luck?
I hate working on Fords, don't ask me about brakes or struts. Ever try praying?
Is the CEL on now (and known to be operable)? Even if it isn't, get a code scan with a high-end scanner, those will read all codes (trans/pending/flags). That may mean going to a shop, not just a parts store, for a scan. But ask at the free places first...