I wish I had a for sure possible maybe answer. Hot oil would be indicative of friction, which would make one think of gear or bearing noise. On a 3kilometer drive, have you tried using a stethascope to listen to the gearbox while driving? The best help I can offer is to direct you to the Fordson discussion forumn, they have people very experienced with the Super Major. At the top of the page it will have a scrolling box for "go to another ..." Scroll down to Fordson, select go.