I think we need more info on the axle, was it stock or is it modified?

Open diff (stock): when slowly spinning with both hubs locked the other axle will spin the oposite direction

Limited-slip/traction control devices (auburn): when quickly spinnining with both hubs locked the other axle will either spin in the opposite direction as an open, sit there or move in the same direction in spurts, also have someone hold the other axle they should feel a tug in the same direction you are spinning your side.

Lockers (detroits): when slowly spinning with both hubs locked both sides will spin the same direction at all times, spinning quickly may cause the opposite side to unlock and you will here a faint clicking noise. If it does spin the same direction have someone hold the opposite side, they should be able to keep that side from spinning and again you'll hear a faint clicking noise.

Selectable (airlocker): will have a threaded coupler to attach an airline to, and I'm not refering to the breather.

Spool: 100% locked 100% of the time, both side will spin at the same time and the same speed and there is no way to stop them from doing this.