Just keeping everyone updated:

I went out and greased the front drive shaft. It didn't make a difference but I could tell it was neglected.

When going for a drive with a tech he was almost positive it was the front drive shaft was out of balance. He checked the tires and said they were great. He checked the drive shaft and still thought it was that. He told me to take the shaft out and drive around to see if the humming went away. He said if there was still a "growling" or "howling" noise then it probably is the pinion bearing, and possibly the drive shaft as well.

I will try to get the drive shaft out tonight, but it might not be until next week.