My theory is that the dual mass flywheel's rubber dampens the harmonics of the spinning parts of the engine in the same way the harmonic balancer does on the other end. In addition, it provides the "give" needed when starting out from a stop or shifting hard.
A sprung hub clutch with a single mass flywheel will provide the give needed but will not dampen any harmonics because the springs are metal and in the end, it's still metal to metal contact and any harmonics are transferred to the transmission.
Why some do and some don't?
Could be the front harmonic balancer has failed or other anomaly in the engine causing excessive harmonics.
I'll definitely be sticking with the dual mass flywheel after reading this thread...
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