Check fluid in the front diff?

 

Could his hubs be locked?

my toyota i built (https://dodgeforum.com/forum/2nd-gen...ry-to-say.html) front drive shaft spun in 2wd with the hubs locked.

 

No locking hubs, there IS the CAD system though, might not be completely disengaging.

 

So the drivers side wheel is constantly turning the side and spider gears in the front diff, and by your discription it sounds like they maybe packing it in, this might be causing your drive shaft to turn at times. Pull the cover on the diff and do an inspection of those gears. And as HeyYou has suggested check your cad.