Hi guys, I just took delivery of a 60" Betstco medium duty flail mower. I'm struggling to figure out how much gear oil the gearbox is supposed to have in it. The manual says roughly 3 quarts, which seems like a lot. A service person at Betstco said that there is a drain plug on the gearbox and that I should fill it up to the drain plug, which makes more sense. My problem is that I can't find a drain plug anywhere! The only access to the gearbox that I can find is the fill plug on top. Does anyone have a Betstco flail who can help me out? Thanks loads!