Is It Posi? (8 3/4)

Put car in first gear, rev engine , let go of clutch. If two marks are left it`s a sure-grip, if only one it`s an open differential. Seriously ,an open differential will be "open" and you`ll be able to look at it and see all of the spider gears as well as the ring gear. A sure-grip will have the center filled with the sure-grip assembly whether it`s clutch or cone style.