Have you seriously established the fact that your dog is bad? Have you tore it down yet? Sometimes these motors jump out of gear, because of poor shift linkage adjustment. I would check that first, before the price of a dog gives you a heart attack.
Yeah, fixing this motor for a friend. Tore the L/U apart and the dog ears are well rounded/pitted. Both sides are bad - looks like someone already turned it around. Thanks guys for the info.