Here is a link to an older post about this same subject.
http://www.peachparts.com/shopforum/showthread.php?t=143093&highlight=eaton
You might be able to get a rebuilt unit from these people for about $600 or so.
Mine was replaced under warranty at 48K for a similar noise on startup
I just hope that it continues to work OK for a few more years.

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Dave
88 300E 250K Sold
2000 C230K Totaled @104K
2003 ML320 156K Sold
2009 E350 4Matic Sport 46K Sold
2011 ML350 60K Sold
2014 GLK350 46k
2012 GL450 55K