You are probably talking about the hydraulic pump - if it is bolted onto the left rear corner of the engine and has a spin on oil filter on it.
It would most like be leaking from the hydraulic lines in the back of the pump - the smaller line is the pressure line and probably the culpret. It could also be at the gasket where the pump assembly is bolted onto the engine. You'll have to look it over to determine exactly where. It may help to put a heavy load on the three point and have someone raise and lower the 3 point as that will make it leak more if it is the pressure line.
Those are outstanding small tractors. Very highly regarded amongst all brands and colors of that era.
Very reliable, durable, nimble, plenty of HP for its size has most of the features found on more modern machines without all the silly safety and electronic stuff on it. You made a good choice for yourself.
