2006 Volvo S40 whine and squeal in reverse only

Have you had the brakes serviced recently? If you have and some other brand other then Volvo brake pads were used then you need to get Volvo brake pads. Now in the beginning of 2004 1/2 Volvo used FOMOCO brake pads and rotors. If you have that brand still on then you need to replace at the very minimum the brake pads because they did squeel pretty loud. If you are still under factory warranty you should take it in to Volvo for inspection and see what they can do for you. Other then that you need to pay to have the brakes replaced depending on if it is the fronts or the rear brake pads making noise.