Did you spin the yoke by hand before you installed the rear end? If not try spinning it with your hand to see if it feels tightness or drag. My guess would be you have a worn out set of gears and there is no cure for the whinning if thats true. It could also be a bad pinion bearing. See if the pinion is loose when you spin it. It may have some in and out movement if the bearings are bad. If you where closer I would give you a hand.