2005 Lincoln Town Car - Whines

I own a 2005 Lincoln Town Car, when the transmission shifts to third gear it starts to whine. The whine is also apparent in over drive. While in second before moving up to third no whine is noticed. Lincoln dealer states no problem with my transmission and thinks the problem is coming from the rear axle

You can always get a second opinion.

These cars do have a rather noisy rear axle.