If you get to the point where the manufacturer will replace car you can keep your same loan. You just ask that the new car be substituted for the old car. They call this substitution of collateral. I did this a few years ago when I got a bad Subaru Outback. They gave me a new car and the dealer arranged the substitution. I was told it was more work and a little complicated but I was able to keep my very low interest loan.