Very bad picture but how can something in the middle of others if not connected move at all?

[img]http://us.f1.yahoofs.com/users/97311675/bc/Xterra/Gen/shaft.jpg?bc1gTD.AxN.z4Xip[/img]

Now in your mind connect the axle shafts to the wheels (this would be when the hubs are locked) Now you have power (wheels turning) to the axle so it will spin. Or connect the drive shaft to the transfer case and again you have power to turn the shaft into the axles, but with nothing on either side to drive them, how do the axles turn?