I second the cerenia tablets- defiinitely worth a try.
I've also found that some dogs seem to settle better and feel more secure in a cage or strapped in in the car?
Fwiw, my own puppy was terrible for the first 5-6 mths or so- drooling like a walrus at the sight of the car. She seemed to settle all of a sudden, and has never looked back, so don't give up hope! (I tried everything and nothing worked for her, although cerenia wasn't about in those days!)
We've done everything by the book/dog behaviourist advise from 8 weeks old accustomising to the car before turning the engine on 30 second journeys gradually increasingly daily (my neighbours think Im mad) cerina tablet homeopathic remedies and even heavy sedation. I've tried the boot back seat front seat alone in peoples arms with my other dog window open heating on and off AC on and off the only thing I haven't tried is the roof rack! The result if we could travel everywhere in a straight line with no bumps/holes in the road and at a constant speed he would not vomit but as we cant after about 10 mins he vomits literally everywhere can one small dog be this sick? The most useful thing I've learnt is do not feed you dog less four hours before a journey I thought two would be fine take my word for it its not!!!! Oh and always sit them on a towel I'm very popular with the car upholstery valet service.
It might be worth talking to your vet about cerenia tablets in most dogs you only need to use it for three to four journeys and then it 'cures' the travel sickness. It's not cheap, but looking after several working dogs in my practice I know that have a poor performing dog is a financial burden.
We have a new sheepdog pup on the farm and she is a lovely little thing,quite biddable for her age.The problem is,that as soon as she gets in the back of the land rover,she is car sick.Even a 3/4 mile trip down the road makes her sick.It has got to the stage that she runs and hides if she sees the land rover door being opened.Anyone have any tips? She has to go in the land rover to go shepherding so we need to get her over it.We've never had this issue before,all our other collies have loved going in the land rover,in fact they'll sit outside it hoping someone will open the door. Thanks.