We had the same noise last week on 98 ML320, 205,000 km. Took it to MB and mechanic said center support bearing was gone. They replaced it and noise is gone. I asked for the old part back and on inspection noticed that bearing section appeared to be leaking out rust so water eventually gets in and bearing fails. At this mileage, I consider it normal wear, especially on a bearing that cannot be greased.

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Vern Lowe