2000 GMC Safari axle may be broken

The problem is that when I put the van in gear (drive or reverse) it does not move. The drive shaft turns. The universal joint turns. The gears inside the differential turn. The wheels do not. I suspect that the rip-off brake repair shop that shall "Just" remain nameless did something to my rear brakes on that side when I told them that I would not be paying them $750 for a routine brake job and to just put everything back together. This was the day before I got to a customer's house and put it in reverse for the last time before it had to be towed home.

When standing next to the left wheel I hear a noise there

I also drained the differential and there was no suspended metal in the oil.

I will be able to check for sure later today but since it is a service van with nothing else fancy going on my assumption would be for a standard one

I just got the wheels off the ground and here is what I found:
(1) if I put the van in drive, without the engine running, the small gears inside the differential turn along with me turning the right wheel (but not the large gear)
(2) if I put the van in drive, without the engine running, the large gear inside the differential turns along with me turning the drive shaft (but not the small gears)
(3) with the van in park, without the engine running, nothing else turns along with me turning the right wheel (not the even the other wheel) but I can see the end of the shaft turning inside the differential
(4) with the van in park, without the engine running, nothing else turns along with me turning the left wheel (not the even the other wheel) but I hear a scraping sound and I can see the end of the shaft turning inside the differential
(1) when I start the engine and put the van in drive The drive shaft, all the wheels inside the differential and the "right" wheel turn (but not the left).
What does that all tell me.