My 1979 FJ 40 just stated making a loud noise under the vehicle. It might be the transfer case. The case is leaking a little bit now and it never has before. The noise doesn't happen when I am driving under 5 mph. It gets very loud when driving faster. The noise sounds like a metal hitting metal that is rotational in nature. It's almost like a piece of metal is out of place and not meshing correctly as it revolves. If I push the clutch in and roll slowly down a gradual grade it doesn't make a sound. Any ideas? I don't know if it matters, but this FJ came from Columbia, South America. Thanks.