Thread: Whats this for??

Hi all and Seasons greetings

While I was under the disco changing the rubber donut on the rear diff I noticed 2 large round bits attatched to the front of the diff with a heavy steel cable connected to the diff housing. I cant figure out what it is supposed to do and why the cable. Maybe they fall off a lot?? whatever it is. Any one know??

It's a harmonic balancer it's supposed to stop drivetrain/chassis noises.