Did it whine like this at all before you swapped the diff? The diff end of the trans does not spin while sitting still so your noise is either further into the center of the trans or even a pulley on the engine which I have heard many that sound like trans noise but isnt. You can buy a cheap stethoscope from most auto parts stores so it may not be a bad idea to pick up one and have the car running while jacked up and lay under it and listen across the length of the trans to pinpoint where it is coming from. MAKE SURE THE CAR IS SECURE ON STANDS OR RAMPS!!!!!!!!!!