210 E300 whirring noise from rear end
 

Guys,
There is a "whirring" noise coming from the rear end of my car as I drive. It has progressively gotten worse over the past couple of months. The noise starts at around 25mph and gets louder as i reach 75mph. It is a consistent sound when I have my foot on the accelerator. It seems like the sound is lessened as I coast at speed anddon't have my foot on the accelerator.
I think it may be the differential or a wheel bearing. I had the differential oil changed 100 miles ago and the sound stayed the same. I switched from my summer rims/tires to my winter/rims tires in December and the sound stayed the same.
Anybody else have this problem? Where can I get my diff rebuilt if that's the cause?

Thanks for any help.

first order would be to inspect the driveshaft and axles.

I would agree with a proper inspection of the driveline to be sure the flex discs, u-joint and center bearing are all doing well.

If so, then zip-tie a smart phone (or other small recording device) near the differential and drive it into the range where the noise appears. Then do the same with it zip-tied near each wheel. That will help you track down the noise.

Does the noise change in frequency (pitch) as speed changes? Wheel bearings are usually more of a cyclical noise (sort of a whooop, whooop, whooop) than constant. Differential bearings and gears can make an interesting assortment of noises.

Still, I'd start with the external stuff that can more easily be inspected, then go on from there.

Good luck.

I am leaning towards wheel bearing (s). Diff noises tend to vary with acceleration/ deceleration. My bearing was a constant drone that Most closely resembled the drone of a B29.
I found someone with chassis ears to isolate teh source of the noise.

Thanks for the replies. I'll work on diagnosing further and report back what we find.

After further inspection, the whirring noise was evident as I was taking left-hand turns at speed. The whirring noise would get significantly quieter when I would turn right. This prompted my mechanic to believe it was the right rear wheel bearing.
Removed the OEM wheel bearing and replaced it with and American Bearing brand. It is a completely sealed bearing as opposed to the OEM which isn't sealed. The OEM bearing was definitely shot. An upside to this repair was that we were able to disassemble the parking brake drum, clean it up, and readjust it. Now it works very well!
Total out the door was $380 including wheel bearing and parts for the parking brake.

Rx
 

Good heads-up advise for we that own 'em, or have 'em in our family. Thanks!

My brakes was making my rear end hum.It was dragging brakes.Check wheels for heat near bearings.But then again could be input shaft bearing.I have replaced alot of thoose,as they sell cheap made bearings to automakers.