I am slowly working through changing all the oils and greasing all the nipples. I am at the back last job is to replace the rear diff oil. I cant see the refill plug, what am I missing? Its looks like a standard rover diff and according to Haynes it should be on the drivers side fron of the diff casting in one of the casting veins. I cant see it although light was poor. Is there some diff without refill plugs and if so how do I refill?