Ford Ranger drivetrain vibration

After waiting for five months I recently took delivery of a new Ford Ranger. It was delivered to my home and the deliveryman assured me that everything was ok with it. That evening I took it for a drive and noticed that there was a vibration through the drivetrain. Initially I thought it might have been a tyre or wheel out of balance, but this did not fix the problem so I contacted my dealership and booked it in. So far they have swapped tyres and wheels, checked out the differential, removed the tail-shaft and checked it for balance. Now they are talking about pulling the automatic transmission apart to attempt to find the problem. I am currently in contact with Ford Customer Care and they have stated that their policy is to repair the vehicle, which doesn't sit well with me, as this is a brand new car that I paid for in full and the Ford technicians cannot find the problem as yet. Can you please help as this is my business work ute and I am unable to perform my duties to the full until these matters are resolved. Am I entitled to a replacement vehicle? Ford hasn't offered me a courtesy vehicle so I am considering going to fair-trading over this matter.