You wanna check the ball joints and front axle ujoints. These are not serviceable from the factory, so they will inevitably seize. A test I perform when looking at trucks with steering issues are as follows.
Get the front end onto a set of axle stands. Have the wheels turned to one side. Then lock one hub manually. Now spin that tire, and if there is any kind of binding, that axle ujoint needs to be changed. Now unlock that hub and do the same procedure to the other side. The only true way to check for seized ball joints, is by disconnecting the tierod from the knuckles and swinging them back and forth to see how tight they are.
I've rebuilt many front axles and have learned that whatever you do to one side, you do to the other...don't just do one side. Also if you have to replace ball joints, the axles are out anyway. You'll actually save money by replacing the ujoints as well. When doing this job, there is a seal that has to be replaced each time it's taken apart, and at $100 each, you should only do it once. Make sure when replacing those parts, you get stuff that is greaseable so you can maintain them.
The Hauler - '05 F-350 4x4 CC Dually 6.0 Powerstroke
The Project - '90 Ford Bronco 4x4
The wife's - '11 Ford Escape
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