I am not sure I understand your question. Are you breaking the balls joints because it is hard to shift, or are you talking about another ball joint that is breaking. The transaxle for the most part is not user serviceable. It would have to be removed from the mower, disassembled cleaned and the new oil added. There isn't a way to just drain and refill Due to grass buildup and water it is not uncommon for the shift linkage on the top of the transaxle to get rusty causing it to be tight and not wanting to move. Clean the grass off and add penetrating oil around the shaft and work it and it should free up with a lot of extra work.