the crank shaft its harmonic balance?

Trilitheum

Just to address an issue brought up in several posts "The rubber annular ring is only about 5mm thick, it can't fix or do ___X____"

This ring sets up a torsional "lag" between the inner and outer cast iron pieces, the thickness along with the durometer of the rubber dictates the response of the torsional damper. This thickness would be calculated to dampen in the target frequency (RPM) range.

The ring itself is not doing to dampening directly, it is coupling the inner and outer masses which as an entire system does the damping it really is a case of the result is more than the sum of its parts, it's how they work together.

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2011 Nissan 370Z Touring/Sport, 6MT, KAD