RE: cen diff cup and part gx12
that pin is what keeps the diff cups centered with each other. to fix it so it wont break again take a new diff cup, wrap a little foil around the large end and take some 7/16 brass tubing and put a 1/4 inch piece over the end. remove some of the foil until it just bearly fits. then put some thin CA glue on it and let it sit for a minute or two. you may need to file down a tiny part of the shock tower to make it fit. once you do this it will never break again.