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Old 10-24-2003, 08:03 PM
JimSmith JimSmith is offline
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Join Date: Jul 2001
Location: Old Lyme, Connecticut
Posts: 3,596
Zoonhollis,

Noise sources rich in harmonics like you describe are usually items with ball bearings. So, the first place I would look is the driveshaft center support bearing. This item is a radial ball bearing with the outer race bonded to a rubber donut, that is then bonded on its outside diameter to what looks like half a pipe hanger for a 4 or 5 inch diameter pipe. When the rubber breaks down water and grit get into the bearing and the isolation the rubber donut provides diminishes and you have a "sound short" to the car body. The body selectively responds to its favorite frequencies so you hear the whole system interacting with the source of the stimulus, the drive shaft turning.

And then, again, it can be the bearings anywhere in the rest of the drivetrain and the front wheels. I would start with the drive shaft center support bearing though as I have had this go out a few times on different cars and it sounds much like your visual description of the noise (pretty good depiction of a noise).

Good luck, Jim
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1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
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