I had one dog that would hyperventalate for an entire trip but at the same time she did not whan to be left home either. For her being with one of the other dogs was most helpful. In such cases she may have stoped hyperventalating and gone to sleep after and hour or two.
given the amount of anxiety and the time you have to work on they following may be helpful.
1, Is the dog anxious approching the car when it is shut of, how bout running.
2. will she willingly get in the car if it is not running? if it is running.
If you are not sure get a book or video on how to read doggy body language something Like "calming Signals" but there are many others in the narket place.
Find out where she starts to feel anxious. Once you know where you can start to desensitize her. The most important point is you want to avoid her feeling axious during the entire desensitation process.
Start slowy reward for calm behavior. do not move to quickly to more axnxiety producing situation. If she show signs of anxiety back off imeadiatelu
While it does not deal specifically with this issue it is a good booklet on the process of desensitation in general CAUTIOUS CANINE, 2ND EDITION
Try taking her on very short trips, with lots of cookie rewards, hugs, pets, etc. just around the block for a week or two. Then lengthening them to longer trips, and then maybe a trip the park for a fun outing with lots of treats and attention along the way. I don't know if this would help or not. Bogie is a great traveler and was from the first day when we got him.
We had a coc-a-poo years ago who had car anxiety. Nothing worked with her, and we just learned to endure her whines, cries, and shaking. We always felt so sorry for her, but didn't know how to help her.
She didn't like the car at all when she was a puppy. She doesn't mind so much anymore. I think it was just the fact that we take her for walks on the river during the weekend. She loves the river, so I imagine it was kind of like a reward for her (same as a treat). She endured the car ride and got the walk she wanted. Plus calming music always stopped her from crying.
Jasper doesn't like car rides sometimes and others, he's OK with it. I try to take him on rides fairly frequently and sometimes we ride to a hiking area and sometimes he just rides with me while I do errands, etc. He has learned that car rides can mean different things and responds to them as they happen, I guess. My suggestion is to take short rides and gradually lengthen them, having things at the end of the ride that are liked.