John Deere 450 ring gear

I have a 450(NO LETTERS) John Deere dozer loader. I was loading dirt using the shuttle shift and sheared off the rivets on the ring gear. Does anyone know how to fix this without tearing the rear end appart? I found all the tappered heads and can push out the heads OK. Can I use some kind of bolt to replace the rivets? It's easy to get to. Is this a common problem when using the shuttle under heavy load? I was also going from high to low with the shuttle pushing virgin dirt. Thanks for your input. cowboy