Hmm found this in google:
Default Re: 3 PTH lift ball replace
Your balls are held in place by a thick washer on one or both sides, depending on ... (Bet you never guessed that ) The washers are tack welded to the arms. Die grind the tack welds to release the ball. Insert the new one and reweld the keeper washer. If your balls are worn out, the easy change systems make a good alternative to replacement.
Hope this helps