I had the same problem with Suzi
She finally stopped throwing up in the car... But, still hates riding in the car tremendously.
What I had to do was always bring a towel . Cover the seats. And than bring anther smaller towel to clean chase up, and puppy wipes will come in handy. Pet Chase a lot, and continue to give him lot's of reasurrance. Try to calm him down all through the car ride. This is very important. Suzi use to pant real hard, but, this is better than getting sick. Talk to Chase too. the sound of your voice will be comforting.
It does get better, but he needs to have more experiences in the car in order to know that he is going to be ok . If he is not exposed to riding in the car than he is not going to become use to it.