Exactly what oldopelguy said... Here's a link to help you visually understand what was going on: Open Differential... Go through the next 2 pages. Open Differentials are pretty weird when it comes to turning. It's supposed to send torque to the wheel with the least amount of torque. To make sure, get another person and have them turn the other axle at the same time, and direction, as you do. It should spin then.