[dandoc]

Did this happen before the new rods and ends? If not, check closely to be sure the rods and ends aren't getting hung up on something (look for exposed bare metal on one or more surfaces).

Otherwise, going off of what you've described, my guess would be the steering gear box. There is likely a broken gear tooth (or more than one). Unfortunately that's the expensive part to break. Do you notice any loss of fluid from the box?

I don't know if a ball joint would create the stick/jerk phenom that you're experiencing. Perhaps someone else is more experienced in ball joint diagnosis. I do know the ball joints are a PITA to replace... had one explode on me as I was heating the metal around it to remove the ball joint; that thing hit me in the arm and narrowly missed the side of my truck.