No I haven't, but they don't use salt on the roads here in the wintertime either. If it's rusted so thin that there are pin holes in it then you are right about replacing it cuz there is no permanent repair for this. Too rusty & thin to weld it. You might be able to skate by with some epoxee patches, but it sounds like it's too far gone & it will be a neverending story trying to continually seal up all the leaks. If the diff cover is this rusted, what do your brake lines look like? I would do a very carefull visual inspection of them front to back because they are very thin to start with, & this could be your next failure.