I'm new to forums, after reading numerous posts you guys provide alot of great information!

Here is my problem, I have a very noticable rattling sound coming from supercharger area of engine at idle, noise is greatly reduced as engine RPM is increased. I replaced all idler and tensioning pulleys to no avail. I also tried removing belts one at a time, noise only went away when supercharger waterpump belt was removed. Checked play in supercharger nose pulley cannot make a for sure determination. Nose cone seal is leaking oil. I was pretty sure it was supercharger coupler until I read numerous post that suggested it could possible be harmonic balancer. Is there a surefire way to determine which one is causing problem? I have priced superchargers on Ebay and thanks to everyones recommendation I will not buy one from 13lucky13. I have been talking to Magnuson Products who claim to be only Eaton authorized rebuilder in USA.
Any ideas would be helpful. Thanks in advance!

take the */C belt off that turn the SC pulley back and forth, if you feel some play, you need to replace the coupler....you will need the coupler and 2 bottles of GM Supercharger Oil

If it'* the harmonic balancer, you will be able to grab the belt and move it enough to rotate pulleys.

Thanks again I will try those two items.

Good. It could be either or both.