Rebuilt 5-speed making noise

[fixkick]

I saw your photo's
and vid.
nasty whine, are you dead sure its the box? using stethoscope. (head set)
all gears in photo look ok.
make sure all engine parts do not sing like that ,sounds like bad alternator to me. (as it runs 6 time crack speed) 6 x 800 is 4800 rpm whine.