1999 Expedition steering?

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 -