Well...I just returned home from a good 200 mile round camping trip. I changed the oil from 10w40 to 20w50, before I left. After about 60 miles of hwy driving I entered the trails. About 2 min In the bearing noise disappeared! Weird. The truck has been running perfectly ever since with no hammering noises.

I forgot to mention in my previous text that this noise began when I realized I had run low on oil. Yes, I'm an idiot! So now I'm beginning to think it was just a sticking lifter....it just seemed so much louder though and the two mechanics that listened to the noise were both certain it was a connecting rod bearing. Is it possible that what ever was making the original noise has disintegrated.