Territory Titanium has a severe vibration

My brand new Territory Titanium has a severe vibration in the rear, to the point that it rattles your teeth. My family won't go in it because it makes them carsick. The dealer tried to fix the problem but without any success. An engineer from Ford looked at the car, and came to the conclusion that it was a characteristic of that model. The dealer then checked other Territory Titaniums and told me that all had vibrations, one was worse than mine. I rang Ford about the problem and the customer service lady gave me a reference number, but that's all I have. I asked the dealer for my money back and they did not want to know. I paid $58,000 for a car that is useless; if I trade it in on another brand I will lose about $10,000. What can I do?