Check the hose that runs from the fill tube down to the lower fitting _ elbow that goes into the gearcase. It seems like there have been several of the hose clamps that were not tightened sufficiently. It seems like the the problem shows up on two or three year old combines, after the hose gets a little dried out and loses some of its flexibility. It conforms to the fitting flare too easily. Oil dripping out of this fitting should be settling into the depressed cavity under the gearcase. It could then be dripping away with crop flow under the discharge beater.