Greg:
(Started to say, "what are you doing on at this time of night?" but you're in Oz, aren't you?)
I'm sure you're right and the flywheel's a node for certain frequencies, but the other masses especially the crank damper and the FEAD are so large that much comes through, and I can even detect some camshaft and geartooth modes at the flywheel! Also tells me a little about clutch torsionals.
For drivelines, I use the same method, but read the transmission output shaft speed via a 12T tone ring, to look at the results of u-joint angle non-cancellation as well as shaft imbalance effects.
- Robert