Hi second post for the day. I have just got a B5100e with 800 hrs,runs well changes gears perfectly, diff lock works, but seems to have a whine/grind coming from the diffs/trann? I have changed the tranny oil to no avail. I am thinking of adding some Nulon Tranny treatment, will this hurt anything or is there something else to do. Should I be overly concerned about this noise or just accept it as part of owning an old tractor.