whil adding 80w 90 gear oil to my rear diff i noticed the sticker says lsd oil only, after calling around i then added the lsd additive is this ok?

Yes.

It's OK, but you should have read the bottle before getting the additive. Almost all GL-5 gear oil already has the LSD additive in it and it will either say "contains LSD additive," or "compatible with LSD," or something along those lines. Very few don't have it. Anyway, adding extra is not only a waste of money, but might make your LSD even more useless. Won't hurt anything though.