I have the same problem with Stedman! I don't know if he really gets "car sick" - but he starts freaking out when we take him in the car with us. He did just fine when he was younger, but now that he is a little older everything has changed. He LOVES to go with us though. Anytime we get the keys and say, "Stedman, you wanna go for a car ride!?!!?" He starts twirling around in the air on his hind legs and barks like crazy and RUNS like the speed of lightening to the door! He LOVES going and gets so excited, but when he actually gets IN the car...he starts whimpering and whining and he yawns literally every 5 seconds!
But I too think it may be my car. I have a brand new SUV (X-terra) and alot of the roads in this town are just CRAPPY and need to be fixed because there are so many bumps. Well, it seems as though any time we hit a bump he gets worse. I don't think he likes the "roughness" of being in the car and going over all those bumps
It's just weird because when he was little, he did fine in the car (it was an hour and 1/2 ride to bring him home when we first got him) so I just don't get it!