You need to give us a better description of what you think the trouble is.
You said, "now sensitive," but I have to wonder if you meant NOT sensitive.

In any case, I would not suspect a speed sensor.

Make sure the tires are inflated to the proper pressure as listed on
vehicle placard (not the max pressure listed on the tire sidewall).
Back when I owned an Expedition the tire store idiots inflated them to
the max pressure listed on the sidewalls and the truck was almost
undriveable.

You might want to join the Expedition Owner's mailing list. See -
http://mail.xpog.com/mailman/listinfo/expedition .

Ed