Mechanical hammering at idle

[TLEC]

I have a problem with some sort of mechanical hammering noise when the engine is at iddle.

It's a 3.8-92.

I have, what I think located the hammering to the "torque-limiter"-thing which means the actual pully for the auxillary belt on the crankshaft.

When engine is of, I can turn the serpentine belt, say 1/4 of a turn on on the alternator, then it stops, I can se on the crankshaft pully that the pully turns the same, then it "engages" the crankshaft.

WHat i think is something is broken in the pulley, any ideas?

[marc-o-matic]

Sounds like the harmonic balancer(crank pulley) is in need of replacement

[TLEC]

After some investigations, I have come to the same conclusion myself.

Is this pulley serviceable, or replace only.
If replace only, what could happen (worst case) with it, while I'm waiting (3 weeks or so) for the replacement.