I have a 2001 F-350 Super Duty with a 7.3 Powerstroke and 4 wheel drive. I bought this truck used back in 2016, and I have had trouble with it wandering from side to side. I have changed everything in the front end multiple times, had it aligned multiple times, changed brakes multiple times, and just about everything else associated with the steering. I previously owned a 99 Super Duty, and it never gave me any trouble whatsoever. I pull several kinds of trailers including an bumper hitch travel trailer. I have gone across two lanes of traffic because of the steering, and now I have to travel at slower speeds just to keep control. I don't know what else to do.

 

Lets start with something simple.
What brand of tires are you running on the front now ?

 

I am using Cooper AT/3 as a set. I always change tires as a set. I have used Coopers on my previous truck with no problems

 

Do you know if anybody checked the rear suspension for any looseness ?

If you have someone move the steering wheel back and forth with the motor running and someone look at every steering joint to spot any looseness that is not found during other work ? That is the better way to check steering components for wear. That way you check the steering box also.