Can an employer force a transfer w/o compensation?

I was hired in Plant A as a non exempt employee. When times are tough in Plant A, the company requires a couple employees to transfer to Plant B indefinitely(usually a few months but some people have been there for years), if Plant B is busy enough. Plant B is located an hour and fifteen minutes away under normal circumstances. They used to pay us our hourly rate and allow us to use a company vehicle to get there and back daily. One day they decided that they would no longer allow us to use that vehicle and at the same time they were no longer going to pay us to travel to plant B. They did say that they would pay one person(mileage not hourly) to drive their personal car and the others could ride along without any compensation. Is it legal for them to not pay us to travel to the other plant? Can I refuse to do this and have a case for unemployment?