300SDL "Ringing"

Recently I've noticed a ringing noise coming from somewhere in the rear of my '87 300SDL at freeway speeds. It's espec- ially evident when I turn an ear toward the back seat area.
I thought it might be a dragging brake, but applying the brakes doesn't change anything. And it seems to me that if the dif- ferential were about to give up the ghost, I'd hear a lower pitched rumbling sort of noise rather than a high-pitched keening sound.
Any idea what the cause of this noise might be?
Geoff
-- "Kwanzaa bells, dashikis sell, Whitey has to pay Burning, shooting, oh what fun on this made-up holiday!"
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I would check the "doughnuts" that hang the exhaust system.
The other thing I would check is the bushings (I think they are nylon) on the rear torsion spring/swar bar behind the rear wheels. Do you get a _clunk_ when your rear wheels go over a speed bump?

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You'll feel the diff and smell diff fluid long before it fails.
Sounds more like a wind noise than anything mechanical to me.
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Need Mercedes parts? http://parts.mbz.org
Richard Sexton | Mercedes stuff: http://mbz.org
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not sure what you might mean by 'ringing', but in the even that you might mean 'whining' rather than ringing like with a bell, it could be your drive shaft support bearing..... does it get worse when cold?
cheers, guenter
Richard Sexton <See http://rs79.vrx.net for address> wrote:

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Whining would be an adequate description. The sound does have a metallic quality to it, though.

Yes, it does! And until you asked, I hadn't noticed that the noise is present when I drive to work very early in the morning when the temps are in the 30s or 40s, but absent when I drive home in the afternoon in 60-70F temperatures.
Assuming the noise is from the drive shaft support bearing, is this something that I should have looked at soon because it could fail catastrophically and without warning, or can I wait until the noise becomes annoying? Is it an expensive fix?
Thanks to all who answered.
Geoff
-- "GHACK!" -- Saddam Hussein
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mine's been doing that for the last few winters.... just appears to be annoying
cheers
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