http://www.hobbypartz.com/98p-25c-1550-2s1p.html one I have
http://www.hobbypartz.com/98p-25c-1800-2s1p.html MIGHT fit as its measurements are almost the same(seems to be a tad taller though)
As for the spur look at it to see if its worn your gear mesh might be off, or something got in and chewed it up with how its unprotected(there is an aftermarket part that covers it). Could be your diff though you might have to take it apart to check it out.