I have just purchased a 2007 Citroen C4 automatic and have noticed a distinct whining noise when the speed is in between 34-38mph. At 35mph the noise is constant. I returned the car to the dealer for them to test and inspect it, but the dealer has dismissed the issue and said that it is not a problem. Their mechanic road tested it and an independent gearbox technician said that as there is no fundamental gearbox issue, it does not render the car unusable. Is this a known issue? The car has a 12-month warranty. Do I have the right to reject a duff car?