Sorry for the newbie question.... but I just changed my rear diff fluid b/c I had a leak around the gasket and I don't know if I should add the friction modifier? I've got a 2001 wrangler sport with 4.0 liter. I'm not sure of the rear axle I have, any easy way to tell? I think I probably have a limited slip but not sure. Should I add the friction modifier just in case or will it hurt if it is not a limited slip??? Thanks