First of all you have no rights to a FT drivers job. You might want to be one and someone years ago might have told you that it would be easier to get a FT drivers if you became a PT Sup first. They lied.
There is a possibility that you could get a drivers job but they are slim these days. Also you wouk d be stating over. Your pay would be what a off the street hire would make even if you make more now as a Sup. You would might keep your weeks vacation but you would be the last one to get to pick which weeks you want. You would get the worst weeks.
If you got hired you would have to make your 30 days if you don't you might not be able to go back to being a PT sup. Just spmething to think about.