you don't get whine from a over fill, you get gear whine from improperly set up gears. I.E. - wrong pinion angle, or too much backlash. if it's whining take it back to who installed your gears
(i'm at my shop right now straightening mine out )
I put a new girdle on and refilled my differential until it came out the fill hole in front by the ds. I put in about 2-1/2 quarts. Must of been too much because it is leaking out of the little vent on the passenger side. I drained a little out and its ok now. No whine or any unusual noises.
I have no whine in my gears. When I filled it up the car was angled and not flat. (The rear of the car was jacked up) So I am wondering if I have to much in. Was just curious if it can cause problems.