[car guy]

The best way to check if it is the clutch disc hub spring that is worn or defective is to lift the car off the ground, Release the hand brake, put the car in gear with the engine off. Turn the rear tire back and forth quickly and listen at the clutch assembly. If you hear the same rattle when the car is running, it is the clutch disc hub assembly that is worn or defective. A poor running engine will ruin the disc hub spring on these cars. If I had it my way I would have the clutch assembly at the engine not at the rear.