I crawled under the truck and I held a stethoscope on the disco with one hand, and I turned the driver's side axle with the other. No clicking noise in the disco.
So I put the driver's side back together, and I went out for a test drive. THE GRINDING IS GONE!!!
It must have been a bad wheel bearing. I put a new Timken on the passenger side. When that didn't stop the grinding I knew the original passenger side bearing was still good. I put that good bearing onto the driver's side and the grinding stopped!
This was a case of the bad bearing being on the opposite side that would seem logical...
And right now I'm going to change the gear oil in the front diff. (again.)