I've just bought a K13 Nissan Micra and it doesn't sound quite right. The noise I hear also seems to be coming from the back but it sounds like when you chop down a gear in a manual going down a hill and the engine revvs, well this is the noise I get in the automatic speeding up and slowing down, even just cruising at a steady speed. It's a drone that just shouldn't be there. Any ideas people? Is the car supposed to be like this? Apart from this noise I love this car.