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Rear End Whining.

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I've noticed a whining noise coming from the rear end of my 08 during a slow turn or when backing up. I've heard some guys with standard GT500s complain of this after a rear end gear change. Is this normal for the 3.37?




YES, it is normal (but not when backing up straight). I believe that you're talking more about a "groan" (dying whale sound) than a a'whine", though most of our KRs are likely to have a slight gear whine as well. The whine is noticeable mostly around 65 MPH. This is why Ford installed the vibration damping weights on the axle.

BUT, the "groan" will be heard when turning tight turns at low speeds. It will do it after you've gotten on the car (put your foot in it) and shifted hard. Cause is from the diff clutch pack being jammed together. The groan will go away again after the car is driven normally (gently) again for a short time. I've read that gently diving tight "figure 8s" in a parking lot will help loosen up the clutches, too. Some people even recommend adding friction modifyer to the diff oil, but I wouldn't, as it just makes the clutches slip more... My .02. There's lots that has been doccumented online about this groan with the carbon fiber diff clutches, and it is nothing to worry about. Learn to love those sounds... ;)


Both my KR and my '08 Bullitt will make that groaning sound after I've gotten on the car, and with both, it goes away again after gentle driving. Both the '08-'09 Bullitt and '08-'09 KR used the exact same rear end.

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A change of rear gear lubricant and addition of a $4 bottle of friction modifier did away with my "groaning" rear end.....actually, it was the car's rear end groaning........I think it's pretty common amongst the 500's.......

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