I have a 2011 4X4 JGC with the 3.6L engine. The parts manual lists two different serpentine belt part numbers - 05184646AC and 05184647AB [XXE]. Does anyone know what the difference is between them? What does the [XXE] designation mean? I googled it with no luck, the OEM parts websites say that both belts will fit, which I don't think is true. Can anyone help?