re crankshaft pulley -- do this ASAP as the mass of metal which running amok and needs to be dampened are the conrods -pistons and crank --the imbalance created by swinging all this mass about often needs to be dampened by a layshaft which rotates in opposite frequency to the crank and both are drilled --balanced - messed with to get metal to stay where it should and do its job --when you have a damper failing it wont fail and do you a favour it will fail and multiply the forces it is supposed to cancel out.. asap. bugs