Thanks for the suggestions! The thing is, I can cause this problem to happen with the truck parked. Standing outside the drivers door and SLOWLY turning the steering wheel from lock to lock. At some point past center, in either direction, the front wheel seems to jump/pop/lurch a little bit in the direction of the turn. I can feel this happen as I drive. At one point this morning, after turning onto a side street, I had to compensate for this problem by holding the steering wheel a quarter turn past center. Then, of course, the steering system "corrected" it's position- leaving me heading for the ditch. When I tried to straighten out the beast, I ended up swerving the opposite way- across the center line of the road. I am going to drive very carefully home and park it until this gets sorted out. It is just to dangerous to drive it like this.
Can this maybe be caused by some fluid pressure fluctuation from the steering pump? Fluid in the pump looks dirty, but doesn't smell burnt. Pump runs quietly with no moans or groans.

John