Hydraulic pump is at the rear of the transmission. This is a NH Plus model with 16 X 16 PS transmission with variable displacement pump at rear of transmission housing. There is no clutch on the flywheel, transmission and PTO are driven by a damper bolted to the flywheel. C3 and C4 clutch packs in transmission function as a clutch. There does not seem to be any hydraulic connection to the engine. My guess is that transmission oil is getting into crankcase thru rear of crankshaft seal. For that to happen, the front of trans may be leaking into flywheel housing, flywheel running in oil and oil passing thru crankshaft seal. Somehow, this doesn't seem likely. Need advice. Or contact with a NH expert.