03 Sedan 4cyl auto. I have a high pitched whine in mine. It sounds sort of like the ignition noise you get through a radio if it is not grounded properly. The first time I heard it I thought that's what it was but when I turned the radio off I could still hear it. Then I noticed that if I coasted or put the tranny in neutral the noise stopped. It also raises or lowers in pitch if you go faster or slower. It's pretty hard to hear and I usually don't notice it unless I listen for it. I can't pinpoint where the noise is coming from but I wouldn't think it was the differential since it stops if I take my foot off the accelerator pedal.