I'm helping a buddy of mine, between us, we have 3 W210 E300's. (2 99's and 1 98)

The oldest car, 150K, has picked up a whirring almost grinding type of noise, that starts at about 30 MPH.... I immediatly thought tire, changed tires.. no joy. So... we jacked it up.. scratched our heads, replaced the brakes.... still has the noise. I'm actually ASE certified, so I"m embarased at this point... now we run it with both rear wheels in the air... no noise. Closer inspection, we figure it's a right rear wheel bearing. after all... that hub is warmer than the other side, and that is the side the noise seems to come from. After replacing the wheel bearing... the noise is the same. So... now we're running out of choices. What could this noise be.

It sounds like a tire.. but not wop, wop... it's sort of whirl whirl, with a little grinding type of noise with it.

My latest thoughts are rear diff. How often do they fail on W210's?

What are your thoughts?

We're going to change the diff fluid, just to look at it, but we're not looking forward to a diff failure. This oldest girl in the fleet has been tough on us the past year, and especially the past few days.

Who thinks they know what this rotating noise is?



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