hello: binq
verifies the location of the pump hyd. if you are connected to the zone box clutch. replacing the seal thereof, is sold repairing kit. it is one of the problems that give us the pumps. other links even see seals and other internal. see level of engine oil for oil hyd. (Rise of excessive engine oil) in these cases the exhaust smokes. These are the possible cases of presence of oil on the clutch zone.
leakage of oil into the engine, the pump is on the distribution and if so you have to see the seals on the crankshaft, by passing through the seal which is the flywheel