moaning noise in 190 E
 

On my 1988 190 E 2.6L 5-Speed I get a moan at around 35 mph and it gets loader until, at 80 mph, it is a roar. The odometer reads 249,000 miles. The car had two new flex discs and a drive shaft center support installed the other month when a new/used differential was installed. Red Line fluid was used in the differential. The rear CV joints were inspected and found to be in good shape. Tire pressure is 36 psi all around and the tires are in good shape. I cannot locate the exact source of the noise, its from the back end somewhere. It is not a chirp nor a high pitched sound, it starts as a rumble-moan kind of noise and just gets louder as speed increases. Last week- end I took the snow tire/wheels off and put the street/summer wheel/tires on. I was hoping that the noise was just the sound of the snow tires (thats what the noise is like - very noisy snow tires). It was not. The noise is still there. Could it be the rear wheel bearings or would they make more of a chirping sound if they are bad (like front bearings can chirp when they need grease)? Any ideas? Thanks for your time.

Does sound like a bearing, but it could be in the diff.

Does the noise change or go away in a sweeping turn (say, an exit ramp?). This is typical for hub bearing failure.
After a drive, one tire might feel notably hotter than the other.
Thirdly, one of the snow tires you removed would probably show an unusual wear pattern- possibly inside edge wear, and perhaps some cupping.

Are you sure it is from the rear?
It can be hard to localize a noise underway.

Best of luck.