Yesterday my 90' Cougar (over 200,000 miles) developed a new sound, I'm hoping someone will be able to figure this out. The sound is similar to the sound that 4x4 mudders make, kind of a whiring sound... it varies with the speed of the car, seemingly louder during de-acceleration. I checked all of the tires and nothing looked unusual. And I haven't been able to pin point exactly where the sound is coming from. I was thinking it could either be a bearing or the rear differential... anyone care to enlighten me?