Taurus shakes at high speeds

My 2000 Taurus shakes violently in the 60mph to 75mph range.

Strangely though, if I get it up over 75mph the shaking goes away, and any speed below about 58mph it drives smooth as well.

Little background: I had it checked out for shaking earlier this year and a mechanic replaced an inner tie rod on one side and outer tie rod on the other.

Car then drove fine, but I might have hit a pothole or two not long after and the violent shaking started again.

I had the same mechanic check it again to see if there was any new damage and he said the everything (tie rods, ball joints, control arms and so on) was fine.

I changed one tire up front an the shaking almost seemed to get worse.


Any idea what is going on here? Why would the shaking just go away when I get about 75mph on the freeway?