D47U. The clutch housing where I engage the pony motor. The oil keeps disappearing. After adding oil, withing 3 to 4 starts it is gone. No oil spots beneath the tractor. Going into the main engine? What is the fix?

It seems about the only place it can go is past the rear starting pinion housing seal & going back in the diesel flywheel housing. Do you have an oil clutch in the diesel & if so it would accumulate in the clutch compartment and if it,s a dry clutch it seems you,d see it dripping out the bottom unless yours has a sealed plug. Lots of them with dry clutches has a hole drilled in the plug & a loose cotter pin in the hole so anything can drain out.If your tractor has a dry clutch take the plug out from under the flywheel if it doesn,t have a cotter pin in it & see if there is oil in there which it shouldn,t.