I have this whine/light grinding noise coming from the engine bay whenever I rev over 3000 RPMS -AND DECELERATE-. If I stay on the throttle, let it shift up, or just ease off the throttle, the whine either isn't audible or isn't there at all.

I had an transmission rebuild about 10k-15k miles ago by a shop in town (never going to a shop again if I can manage it), so the tranny SHOULD be in great condition... however I hear stories about shops using the wrong fluid (dextron, anything other than atf +3 / +4) and that sometimes causing a whine in the transmission... could this be my problem? I also hear the whine when I rev in Neutral (honestly to me it sounds like the engine noise is shitty, but I'm hoping its froming from the tranny area)... If you think this sounds right along the lines of my problem, I'll prolly do a tranny flush this weekend (3-5 gallons of fluid needed right?)...I hope there isn't any permanent damage, that rebuild was a costly ripoff both in time down and money...