I've been hearing a strange mechanical noise recently when the car is in first and second gears and I can't hear it after about 30 mph. To me it sounds like if you stick a playing card in the blades of a fan, and the frequency is coincident with the rpms. I ripped out the back seat and put my ear to the floor while it was doing this and it seemed to be coming from under the rear seat, perhaps more on the driver side. Someone unfamiliar with mercedes suggested maybe it was the Universal Joint but with the single-piece mercedes U-joint that seems less likely. Any ideas? I've done some repairs but am pretty much a Mercedes novice, so any help would be greatly appreciated. Thanks!

 

does the sound change when you let off the throttle? change in turns? or any other information so i can narrow down the options.
initially i am thinking cvshaft but with more information we can pin it down easily.

 

HI

I too having the same problemwith my1984 SDand it makes a whirling sound,the soundchanges when the acc pedle off, do u think is the CV shaft or universal joint??? (info: SOUND STARTS AT 40MPH and FADES AT 70 MPH but still noticiable)

Thx

 

Don't forget to check the rear wheel bearings. They're hearty, but they do eventually wear and could cause the kind of noise you describe.