We adopted our 5-year old mutt Milo 4 years ago. He was a bit unsettled in the car when we first got him, but we thought it may have been related to the stress of the shelter/adoption/new surroundings, etc. However, it continues and is an issue with every car ride. He never gets actually sick but shakes and drools any time he is in the car. He never balks at getting in the car, has never vomited, and is always happy as a clam once we arrive at the destination. It doesn't make a difference if he is in the front or the back, windows open or closed, in a crate or just seatbelt & harness. Also, no difference if he is in a car or truck or RV. He is marginally better if someone is right beside him, but not much.
We have tried Rescue Remedy, CBD, Gravol and a Thundershirt all with some initial tiny success but not sustained. Now, with the vet's recommendation, we are now using a combination of low doses of Gabapentin and Trazadone for longer trips (over 3 hours or so). He is basically calm (no drooling or shaking but not completely stoned), although we do find it takes a little while to wear off at the end.
I had one day recently where he rode in the back seat with his head out the window as happy as a clam and I have no idea why that one single trip was different, but it hasn't happened before or since.
Any suggestions?
Picture of the goofball in his normal happy state (no pics of sad traveller!)