Its very possible normally from Christchurch Airport to Auckland airport that you have ten days plus a free ferry crossing for the vechile. To drop it off at the Auckland Airport. You will have to put down a 1000 dollar deposit as well pay $5 dollars a day. You will have to of course fill the campervan or motorhome with pertol buts thats all. Great way if you are in the hurry and want to get up to Auckland cheaply.