HAWAIIZR-1

Rich,

Just a Kb7tif mentioned, I think from what I have heard the rattle is inevitable even if slight. A friend of mine here has the light weight flywheel with ZF6 on an LT1 and I can barely hear his if at all, not to say that mine will be the same. Another friend of mine that has a new Porsche 911 had the same results with the lightweight flywheel and even thought his rattle is more pronounced, I can live with it. I think the subject has been beat like a dead horse on other threads. Here is what Bill B from ZFdoc has to say about the noise:

The "at idle gear clatter" with LT5 engine and light weight flywheel
combination can range between "not that bad" down to "really bad" depending on the health/integrity of the ignition system. The
slightest miss in the ignition system will cause gear clatter to really be
present. There are a few tricks to minimizing this occurance of gear clatter:

1) Go through the transmission's main bearings setup to make sure that
the very thickest shim possible is installed at the front and rear main bearings as well as the counter shaft front main bearing with the retainer clips fully seated. I know this really helps based on experience. This takes
about one hour and $100 in small parts, gaskets and new oil.
2) replace the four of the eight coil fasteners with nylon fasteners which eliminate the coil's propensity to develop shorts at the coil plug-in lead ends.
3) New coils/wires/plugs are always better to do this with if they aren't already new.

He added to state: Ace Hardware sells nylon bolts the same thread size as the OEM coil fasteners (8 total). Take four nylon bolts and cut them to the correct length... results in lower propensity for the coil to seek/develop an altered ground path through the least durable portion of the coil at the fastener lug between the coil leads.