Hi ThereCustomer The part is called a Harmonic Balancer.
It is located on the front of the engine and 1. has a main section that is bolted to the crankshaft with metal grooves in it which tells the computer which position the motor is in. 2. Has a rubber section that absorbes engine vibrations and 3. has an outer pulley that the drive belt is run by that works the power steering and air con and alternator etc.
Anyway the rubber has broken and the inner and outer are clanging together.
If it were my car I would change 1. the harmonic balancer 2. the crank angle sensor and 3. the timing case seal. Depending which model commodore exactly the part usualy can cost up to $ 150 for the balancer and $150 for the sensor and the seal plus some labour about 1.5 - 2 hrs.
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