Check the kingpins that are holding onto the knuckles. Make sure that you do not tighten the kingpin screws.
Also, check the Ball cups that are holding to the Ball ends to make the steering work. They could be binding, or holding too tight to the balls.
No pun intended.
Hmm... OR you could be driving too fast that your car is holding onto its balls. I mean Ball Ends.
ALfie