Window stuck

I have a 1997 V8 4.6L Ford F 150 supercab truck with power windows. The driver's side window is stuck in the up position. When you push the button to roll the window down, nothing happens. I took the window motor out and the motor works when it is not attached to the window gear. The window can be pushed down or pulled up manually but it is somewhat difficult. Is seems to me that if the motor will work without being attached to the window gear that something must be binding the window. Before the window stopped working, the window motor sounding like it was straining when pushing the window all the way closed. Could the motor be bad even though it works under no load or is something wrong with the window gear?

Thank you