Anyone have an opinion on this? I had the rear diff gasket replaced due to a small leak. After two days the half shaft seal on the diff and gasket were both leaking and brought back again.About a week after that I started to notice a vibration in the car at 40 mph only when the car was first cold.Then it would go away.Now I noticed the vibration at higher speeds and a howling sound at 90 mph only.Sounded like it was coming from the rear or maybe a tire. So I had the tires rebalanced and rototated. Nothing changed. I m wondering what could have been messed up on the first two repairs? My 1998 e430 currently sits back at the dealer. Any ideas so I can be ready when they call? Thanks

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98 E430(sport), 99 ML 320 (sold) , 05 C 230(sport) Mark