2006 E350 4matic driveline vibration
 

My 2006 E350 has a driveline vibration, occuring only when the engine is still cold and when accelerating up to freeway speeds. It persists for about 5 miles and seems to go away when the engine temp. reaches normal. At 3000 miles the transfer case was replaced under warranty. Apparently there was a recognized problem with the transfer case with this model. Could this be some other driveline problem? Should the transfer case be replaced again? I've had it to the dealer three times without identifying the cause. The car has 31,000 miles on it at present. I don't think the vibration is getting worse.
Thanks for any help,
KEH6444

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