There should be an aluminium plate retained by the fill plug that talks about the special additive required for the LSD.If its not there you either dont have an LSD or the diff was not modified(new seal and additive) in service. I belive the additive is in all late model diffs and it was only the early series 1 that had the mod done. The series one had the thin discs, 13mm wide I think.
Phil
