Sounds like you have a 1997 or later C280? ASSuming that is the case then get back to your local dealer & complain about this problem! They might(should) get you some GOODWILL help on this problem.
One of the biggest problems with this trans IS MB says that they have LIFETIME fluid fill. And if you want the lifetime to be less than 100K miles you WILL believe that. Otherwise have the trans serviced!
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