Don't feeding the dog 6-8 hours before a car ride, I used to have to do that with my cat Dusty for travel.

Also try working up to car rides. Start with just sitting in the driveway, car not running until the dog is comfy with that. Then try just starting the car and still sitting in the driveway until the dog is comfy. Then try short 5 minute drives around the block until the dog is comfy. Then gradually increase the driving time each trip out. Take several weeks or more to get this process going based on your dog's attitude to each step. If you go slow with each step and make it a positive experience for your dog you should have a good travel dog in a few months.

If things are just not going well check with your vet, there are tranquilizers available for travel they can prescribe, but most will recommend trying the above things first if you aren't going to be traveling a long ways anytime soon.

Good luck.