Have you tried visually identifying the geometries, like a visual trace? If you're trying to spin wheel 3, are you sure its wheel 3 you are referring too? For this kind of stuff I usually do:
var traceMat:WireColorMaterial = new WireColorMaterial(0xFF0000);
for each(var face:Face in theMeshIThinkIsTheWheel.faces)
{
face.material = traceMat;
}
