Eaton and Meritor hasn't used a gasket on the 3rd member for many years. They use RTV silicone. We couldn't afford to use gaskets on our trucks anymore because the gaskets always weep and we would be written up for oil leaks. Use some Permatex RTV and you can forget about it. If you are worried about originality, just scrap the excess RTV off with a razor blade and no one can tell the difference.