How to determine if it is the carrier bearings or pinion bearings???
 

I have a 2006 2500 Mega cab 4X4 with 112K miles. I am hearing a low speed noise (like a caliber grinding on the rotor) but it does not change if I lightly aply the brakes so I have ruled out the calipers. it is speed sensative....the noise frequency goes up and down with the speed of the vehicle. Most noticable when at low speed (going through my neighborhood)...25 MPH. It is not affected by turning the vehicle left or right so I have kind of ruled out wheel bearings.....plus it seem like it is coming from the rear. I will check fluid levels tonight and report back. I have done a ton of searches here on rear end noise and it seem like it is the pinion bearings or the carrier bearings.....just curious as to how do you tell which is the culprit???

If you can put it on jack stands safely, have a helper run it in the air at a speed where you can duplicate the noise, then climb under the truck with a stethoscope, you may be able to pinpoint the noise that way.

I would also check the emergency brake shoes inside the rotors. Is there any chance they could be dragging, or be full of debris? Does the noise change if you apply the emergency brake while going down the road?

Never thought about the E Brake dragging....I never use the E-brake...almost afraid to put it on now....might not release. These are also my original rotors with 112K on them so there could be debries in there. Will check tonight.