My old dog was like this. On a motorway stretch, he'd calm down, but as long as we were speeding up and slowing down or going around bends and changing gear, he'd whiffle and howl. He was like that his whole life.
What did help was making the space he travelled in bigger. In the back of a hatchback with a dog guard, he was much worse. If you took the dog guard out, his anxiety visibly reduced. In the back of a van, he'd be distressed because he couldn't see out. Riding in the open back of my pickup, though, although he'd rarely sit down, he could roam around and look out of the sides and would stop making such a row. (He jumped out, just once, and got lost for 12 hours; he never did it again!)
The quietest and most relaxed I can remember him, in a car, was when I got a lift home with my boss in his estate car. The dog sat in the boot and seemed perfectly relaxed and quiet.
I don't think it was my driving....