I have am 04 Ram 1500, 4x4, 5.7l hemi, 61k miles. It started to days ago. My truck started making a whirring noise coming from the rear of the vehicle. I notice it at lower mph when it is not drowned out by engine noise. I can hear it during acceleration and deceleration. It is louder when I accelerate and then quiets and lowers in pitch as I decelerate. It does not get louder when I turn so I dont think it is an axle bearing. I am unsure if this is a pinion bearing, carrier bearing, maybe a race or LSD clip popped out. I dont know. Is there any way to diagnose a diff problem without digging into it? Also when this started we had a temp drop to -50 below zero. Could this be a cold related issue? Any help would be extremely appreciated. Thanks in advance for the help!