The ball and socket part of mine came apart so I was able to put vise grips on the ball end, even with that it turned pretty hard, if you've got the bushing end out of the sway bar try breaking the link if you're not re-using it, or try to grab the 5/16 part with vise grips and turn the nut with a wrench. Please note that those puppies are expensive if you need to buy one, almost $50.