Hi guys, thanks for all the good ideas.
Our trips can be quite varied. For example, on Mondays and Fridays, I drive my wife to work, and often take him with me, and there are other, longer trips, some lasting a bit over three hours, where he usually sleeps (except for when he's having a ball, taking in the sights -- like the people in the car next to us at the lights).
I dont think completely retraining him is an issue, as he is still for the most part, fine around cars. I will have to try Smoothiegirls suggestion, and try other cars. Hopefully by Friday I will have accomplished this (what, with working and all).
I will let you know how it pans out, til then, I will keep him out of my car - just incase something is hurting him.