hi i have a defender 90 200tdi with a worn transfer box . a friend had a low milage transfer box from an automatic .when i fitted it it had an intermittent drone noise in 5th gear it would drone about every second .2 years later i fitted a new chassis and i also fitted a rebuilt r380 gearbox and axles with good diffs .i still have the drone noise (i can feel it through the body of the car )has anybody got any ideas about what it could be or is it a recon transfer box ?