Well, I had to replace my brake master cylinder yesterday and got a chance to inspect the axles. The left axle seems to be locked up. I cannot move the shaft at all. Now I'm certain that the left axle is the source of the noise. The right axle is leaking grease out of the outer "can" but the shaft can be moved and for now, I don't hear any noise from that end. It looks like I'll be taking both axles out instead of one.

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2001 Dodge Ram 2500 Cummins Turbo Diesel - 4x4, auto, 3.54 gears, long bed
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