Hi, I have a 27 Regal Commander Big Six EW sedan. The starter motor goes around just fine... won't engage the crank. Tried to remove it to examine the parts to determine the problem... but after removing the fan pulley and the front with the clutch pieces, I can't remove the rest from the crank. The nut came right off. As I try to pull the back and sprocket... it moves about 1/4 inch and comes to a hard stop. I don't want to apply force... don't want to break anything. Suggestions? I still don't understand what drives what and how the starter disengages from the crank after the engine starts. Help!