2000 Ford Excursion suspension problems

Defect in suspension system of car causes the car to move laterally on dry pavement as if the car were hydroplaning. Happens when the vehicle encounters "washboard" or rippling in the pavement. I suspect that the suspension is too tight since it does not seem to be as bad when the vehicle is loaded, weight seems to help the issue. All occurances (4) happened on highways within 5MPH of speed limit on dry pavement during optimal weather. My wife is afraid to put the children in the car and drive it.

Dt*: the contact stated the suspension: front control arm: upper ball joints and the suspension: front control arm: lower ball joints had prematurely worn out. The old parts were not manufactured with grease fittings as were the replacement parts. The upper and lower ball joints were replaced by an independent mechanic. The manufacturer was notified.