Should front driveshaft spin in 2wd?

[hemi43]

No, the shaft should not be spinning. If it is, most likely something is binding in the transfer case or hubs.
Jack the front of the truck up and spin the front wheels by hand. If the driveshaft spins, then you know there's an issue with the hubs. If not, you will need to remove the transfer case and investigate.
Unless you can drive this truck in space, that diff will never see any vacuum in it.