I have a e350 2009 (C207). Under heavy acceleration I get a loud viirrrr noise, similar to the noise of being on an aircraft that powers on. It is not there at idle, cruising or when normal or slightly heavy acceleration. I have changed the transmission oil which eventuated in very smooth changing. I have also cruised in neutral and no noise, reve'd the engine in park, no noise, it is only thereunder heavy acceleration as in foot to the floor but it is very load noise. Does not sound like grounching, clicking, grinding or even metalic. Hoping for help as I'm stumped.

 

moved to C207 forum...