300SDL. Weird sound from transmission output or wheels
 

The sound is a bit like I am driving with off road tires. It is depending on absolute speed, not engine speed. I can hear it more clearly when release the gas pedal and the engine is more quiet.
Can it be the front wheel bearings or something with the drive shaft?

could be that, brakes dragging. Flex Discs carrier bearings (if equipped) Try to isolate where the sounds are coming from. front, mid, back. Left side, Right side etc

Wheel bearing.

I recently had the same noise. Replaced the bearings, no change. Now doing the calipers. Condemned the bearings too quick.

Is there a proper procedure to test the front wheel bearings before removing them?
Someone said there should be a 0.02mm play if they are correctly adjusted. But I don't know where to measure the 2/100mm? I guess axial play at the center of the bearing?

Unsure why a caliper should make a noise like that?

It is hard to tell where the sound is coming from. I'd spontaneously say front right but I could be wrong. A stethoscope could help but I don't know how to apply it during driving.

What exactly are dragging brakes?

Car has 330K miles and it might be time to change wheel bearings anyhow. It it is not this I'll move on to the driveshaft. I'll inspect the rubber boots at the driveshaft and axles first. Boot failure should be obvious.

I agree, I changed the right front bearings with no result.
Did you have ant luck with the calipers?
What exactly are you doing with calipers?