2003 Dodge Dakota rear differential whine

03 Dakota 2wd reg cab. 8 1/4 rear LS 355 ratio. Between 55 mph and 50 hear whine on deceleration. Between 60 mph and 70 hear whine on acceleration. Fluid in rear is full. Ruled out tire noise. Dealer has been in rear twice, changed ring & pinion. 1st time took care of deceleration whine, acceleration whine started. 2nd time both whines are back. Took to another dealer, changed housing with gaers already set up, installed old axles, backing plates, and drums. This rear has exact whinning sounds Can you please give me your take on this? Thank You Mike