Spindle bearings?

I assume you mean the roller bearings in the hub body. I have never been in any truck which makes this noise when it gets cold. The bearing are always rolling. Why would the sound stop when I unlock the hubs?

My second though is about what the dealer told me. Frozen grease balling up around an axle shaft. Now that I think about it how could that be possible? The shaft is on the other side of a seal where the lubricant should be differential gear oil. I hate car dealers.

The temps have moved up to about 15 F and now it's not doing it. It's around the zero mark.

This is strange.

Since you went to arctic grease, did you have the same thing happen?