Whistling sound coming from right rear - 2004 Ford Taurus

Checking Window Seals - The window seals (weather stripping) in your car are used to seal the water and wind for entering the passenger compartment. When these seals fail from damage or are eroded by the weather they can allow wind noise to enter the passenger compartment. This failure can cause a whistling noise as the car is driven. Some noises are only present when the vehicle is driven at certain speeds such as 55 MPH. These whistling noises can be difficult to find since you are driving at the time. Have a passenger help with the diagnosis by running their hand along the area the noise is being generated from. Once the noise source has been located replace or repair the failed seal and recheck.