I had a question about this recently. Sorry -- I lost the specific email into the mists of my Inbox, but anyways, here is my answer.
My dogs travel all the time with me in the car. They come along to dog shows of course but when they are little I bring them along on bank runs (the teller always gives out biscuits) even long before the puppies get to come along to the park.
Most of my dogs love going on car rides. But not Barbie. She was terrified of the car. Came out of her crate drooling so badly that she had looked like she had been under a hose.
To help her (and me), I started putting Barbie in the car in a gradient. First of all, I never put her in the car loose, only in her crate. A crate trained dog treats their crate like a security blanket. So first I put her in the car in my drive way for 5 minutes. Then I made it longer. Then I took her with me in the car. Not long trips, just around town. It was important to do frequent small trips. It was also important not to coo and sweet talk her in the car. I've always found that cooing tells the dog that there's something wrong. Eventually Barbie drooled less and less, until she stopped. She was never thrilled about car rides, but she ceased being terrified.