A320 driver

My Colorado has a clunking sound from under the rear end. Dealership said it’s normal. He said the rear axel is free floating and that’s the sound it makes when you travel over uneven surfaces. Sounds horrible, but they checked everything to make sure. Is this true? Is this what a free floating axel sounds like? Somebody else told me it might be the leaf spring package. Im not a “ car guy “ but this sounds logical too. Any info would be appreciated. Thanks