It could be the stator lock? but they don't screw up very often. Is it sluggish off the line or sluggish when you get it up to HWY speed? The knocking noise could also be a cracked wafer plate, they can make some strange noises. Take off the inspection plate and take a good look around. If all else fails get under it and listen. if it makes a knocking noise when you put it in gear and give it a little juice while holding the brakes its probly a rod.