Actually, that would seem to tie the whine to your overdrive gear.
My first reccomendation would be to change the fluid and filter. Maybe even have it flushed, and the filter changed, so that all the fluid is replaced. See what that does for the noise.
It doesn’t seem to be harming anything so you can probably ignore it for the time being. But I think a full transmission diagnosis will be the only way to determine what the problem is. Since it seems to be related to overdrive gear, I’d say that the TC is probably NOT the problem. But I could easilly be wrong.
-Matt