I have heard that if the shaft won't move in or out enough to go off of the seal surface, you don't need a tack or a clip. On some lockers and LS's, they don't have the cross pins inside like the stock ones do. The Martack is used on these diffs, because otherwise the shaft could slide in past the seal surface. I also have heard that the detroit has the cross shafts so you shouldn't need them in there either. My thoughts are if you can keep from tacking them, it makes it easier when you break something to just slip off the birf rather than have to grind it off.
