2000 Dodge Dakota Whine in transmission

I have a very noticable whine in my trans. In all gears but over drive. The shifting is perfect but this whine is there from 1st gear right up until it shifts into od.
the pitch of the whine doesn't change with gear shifiting but rather with speed of drive train.
If I put it in nuetral and shut the engine off to coast, it is still there. When it shifts into od, you can here the shift in the whine and then disappear.
In other words, when the trans shifts into od, the tone of the whine will change with the shift and go away.
Any help would be appreciated.