Pitman arm

[Nukes16]

I've replaced everything in my front end at least twice, inlcuding, the steering box, the spindles, springs, ball joints, and idler arm. I've had it aligned 3 times, today will be the 4th. The only thing I haven't replaced it the pitman arm. Can the pitman arm seize so that it doesn't turn, or is difficult to turn and won't return back to center?
My wheels are easy to turn when the truck is jacked up but they don't turn well under load??
Any suggestions out there?

Thanks in advance