The pivot ball is located inside the steering knuckle, and attaches the knuckles to the a-arms. Its not that the pivot balls fall out. The problems you were experiencing indicate that the pivot balls were never set correctly. Tightening them brings the knuckle closer to the arms, which in turn pushes the driveshaft farther into the cup, allowing full suspension, and no need for limiting straps. Hope this helps out...... for your next build?!
