I purchased this car brand new in January 2006 and didn't notice any noise until November 2006. Every day it is cold outside the noise comes back and now it's worse than usual. When I first start the car and back up, it's really loud the entire time I'm driving until it warms up then it stops. I took it into the dealership four times. The first time they told me they had no one available to look at it and for me to make an appt. and bring it back. The second time I requested someone ride with me so they could hear it but when they did, there was no sound made. Apparently the car had warmed by the time I drove it there. They found something wrong with the floor board on the driver side and said that could be the problem. They ordered the part for that and repaired it weeks later but still the noise is there. The next time I brought it back they said that it was just how the car suppose to sound when it gets cold outside and as long as there were no lights on (check engine, etc) then everything was fine. Said I could leave it overnight and they could check it first thing the next morning. I asked if they could give me a rental since this was the only car I had and I couldn't leave it for having to get the children to/from school and me to work. They said they don't have that service and that's all they could do for me. I am very unsatisfied with Nissan. I have been having problems with that car since I've gotten it and I thought they were great to work with but that was in the beginning when I first purchased the car. A few months later they started acting differently.