Yesterday, I changed the engine, transmission and drive train fluids (engine oil, transmission, and rear shaft housing, final rear drive). The transmission and rear shaft and front shaft drive all require the same weight of oil, 80W-90 hypoid gear oil. The surprise came when I emptied the rear shaft housing oil. It was a milky yellow color. The transmission and the rear drive looked like what I expected, golden yellow. This is the second time this has happened. Can someone explain why the rear shaft housing oil looks so different from the transmission and the rear drive oil? Thanks.