got a lurcher pup that did exactly the same thing, asked about ,even thought about buying the herbal remedies , its 9 mounth old now and has really improved, all i was doing,start with plenty of short trips , and let the dog clean itself before hand ie small walk out, dont feed prior to going out,gradually increase and on a med/long trip stop half way and let dog out , this is working for me, i often let it in the van when not in use and give it praise and a odd treat, barry