I've had a growling noise coming from the rear end of the truck for some time now. It was pretty mild at first but in the last couple weeks has gotten loud. I can hear it as slow as ~20 mph and it gets louder with speed. If I let off the gas or put it in neutral while on the highway, it gets much quieter but it doesn't go away completely. I just took a 6 mile trip on the highway, up to 60 mph, and got under the truck to feel the diff. It was quite warm, especially in the front. My friend thinks perhaps my pinion bearing has gone south. We were inside for about a half hour and then came back out and made the same 6 mile trip back here and it felt even hotter.

Recommendations?