Car Anxiety in my dog

Question
My husband and I adopted our 1 year 4 month old Boxer/Lab mix about 6 months ago. When we picked him up from a town almost 2 hours away he showed no anxiety in the car at all. When he rides in my husbands car he shows verbal anxiety but does not make a mess as long as we make sure he has had plenty of opportunity to do his business before we go anywhere. However when I take him in my car he gets very anxious. He approaches the car eagerly and starts the ride with enjoyment.  However within 5-10 minutes he shows signs of anxiety, whining, pacing, some drooling.  After 10-15 minutes he vomits in the car, and when I pull over to walk him he has what appears to be very uncomfortable diarrhea. I don't want to cause his anxiety so I rarely take him in my car and when I do I make sure it is a very short trip, and we don't take him in my husbands car much either as to not cause undue stress. I would love to take with him more often but I hate to make him sick. What can I do to ease his discomfort and stress.

Answer
Your dog appears to be anxious when you are driving (NO REFLECTION on your driving skills lol).  This suggests he is not as emotionally confident OR that you are (more likely) somehow involved in taking the dog places he would rather not be: groomer, vet, etc., OR (less likely but possible) the same sex (yes, dogs are aware of which sex humans are) as a person in his past history (who possibly dumped him or took him to the kill shelter).  I'm unsure what "verbal anxiety" means except that the dog is vocalizing: perhaps whining, maybe barking, etc.  YOU may be misperceiving this entire thing: you and your husband are most likely taking longer trips together.  It's VERY common for dogs to vomit in the car; this is the result of motion sickness during puppyhood which persists into adulthood.  It's clinically proven that anything causing vomiting in a dog ONCE will PERSIST in doing so.  What YOU DO when the dog begins to exhibit anxiety can contribute to it; many people (out of kindness and concern) will attempt to calm a dog, talk to the dog, pet the dog, offer the dog treats, all of which makes the matter worse.

TEST: let your husband TAKE YOUR CAR out for a ten minute ride (with the dog, naturally) and see the result; then YOU take the dog (immediately after) for the SAME ten minute ride, and see the result -- then (next day) REVERSE: you first, husband second.  This test allows us to determine what the culprit actually is: the ride itself (if this is the case, the second ride will be worse no matter who's driving) or the association with the person driving.  At your first available opportunity, remove water from the dog (for test purposes only) one hour before the experiment; be certain he has had a bowel movement that day (this will determine the time of day you perform the test) within a reasonable time before the test run(s).  Give him absolutely NO ATTENTION in the car (both human participants) regardless of how he behaves.  Report back using the followup feature.