Checked the level in my gearbox the = other day, and was wondering again about the GL4 GL5 question. Is it possible to = tell if the box oil is the corrosive kind just by smelling it. I noticed that = the oil didnt smell of sulphur, whereas the normal smell of normal EP oil is = pretty overpowering. Plus, if my gearbox is still with its original oil, what = did they put in at the factory in 1987?