My 08 mustang gt has recently started making a loud high pitched noise from the rear. It only makes the noise when going above 15 miles per hour so I can't really listen outside to tell for sure where the noise is coming from in the rear. It is a constant sound when at that speed and higher, coasting, accelerating, braking, etc. I've tried bouncing the car up and down and there's no suspension squeaking. The past owner said he had to replace the passenger side rear axle seal. Could anyone help me identify this noise?