When you took the main gear off the cup that holds the little gears was there a small rubber seal around the outside of the cup?If so then your diffs are sealed.If it didn't then it is not but want you can do to seal then is use some RTV sealant around the seam where the big gear and the cup connect.Just use a small amount and apply it like your resealing the edges of you bathtub.Hope that helps.