I had dark oil coming from the clutch housing and figured it had to be main seal. Split tractor and replaced friction disks, pilot bearing, throw out bearing, rear main seal and adjusting bolts on clutch fingers. Put it all back together and started it up. With clutch pedal fully depressed all was well. Started releasing clutch pedal and about halfway up there was a serious knocking sound. Clutch pedal fully released, the knock mostly went away. Then the oil leak came back. Anybody else experience such a thing? Ideas on what went wrong?