If the rubber gasket on the harmonic balancer is ripped up will this cause a bad knocking noise How do you replace it if need be?
Hard to say. However, if the "rubber gasket" you're talking
about is the center bushing on your harmonic balancer, that could
throw your Harmonic balancer out of balance. This could easily make
it shake to beat the band which in turn could be the knocking noise
you're hearing. I suggest you get it looked at immediatly. If that
is what happened, your engine won't survive long.