Originally Posted by Brent

Log onto the forum with your user name and password. The page heading will update and will now include a Search button. Hit the button and in the drop down menu put in "differential whine", "differential noise", or "humming noise". You'll call up a number of posts that describes this problem. I haven't gone through every one of them so I can't say which is the best to read so plan on peeking at a number of them.