I tried searching posts in the steering sector but didn't find my problem listed?
I've got a 91 F-150 5.0/ E4od 4x4. XLT Lariat About 6-7 months ago I had a little play & wander in the front end so after checking the ball joints & steering linkage, everything was up to par there.

So I started adjusting the steering sector screw clockwise 1/4 turn, then test drive, then another 1/4 turn & test drive until I had turned it 1 full turn & the steering seemed to be just right? I mean going down the highway at 70mph & it steered perfect, no play no wandering, it handled real well. So I tried it out on some 2 lane back roads & it handled fine, took the curves with no problems. Now about a month ago I started noticing that it seems to be getting tighter & harder to steer, like the pump isn't giving me the power assist it used to, & it doesn't seem to want to return to center after taking a curve, I have to manually bring it back. So today I jacked the front wheels up completely off the ground & without the motor running tried turning the steering wheel to the right & it took both hands, but on the return it was real easy till I got almost to center & then I had to use both hands again, I did this turning it to the left & it was the same thing again, so I centered the wheel & went & tried turning the drivers side wheel from the wheel itself, it was impossible to move? I then turned the wheel all the way to the right with the steering wheel & I was able to pull the wheels back to almost center & straight before it tightened up & couldn't move it again till I turned the steering wheel with both hands. So now, I back the adjusting screw out 2 full turns & try the same movements & there's no difference? Also while turning the wheels back & forth, Fluid was purging from the fill spout on the pump, I had to refill it with about a 1/2 pint? I took the truck for a drive & it didn't help anything. Does this sound like my steering sector has went south on me?