Should rear axles (both) being going out on my car? on 2008 Ford Mustang

Ford Dealership claime it was my tires. I purchased new ones. Then they said I needed an alignement so I had one done. Then they replaced my two rear axles but the noise of a thump thump can be heard from the rear.

Asked by for the 2008 Ford Mustang
When you do you hear the noises? What does it sound like? Could be the carrier bearing in the differential. What gear oil did they use? This is a very simple design and not many problem areas.