The Viper engine has quite a bit of low end torque, extraordinary for a gas engine, similar to a diesel engine at idle. Typical diesel trucks with a manual transmission require a dual mass flywheel to absorb the vibration (2 piece LUK flywheel w/springs) in order to be quiet at idle in neutral. The springs on your clutch disc are there for a similar reason, to absorb the axial pulsations and action on a hard shift, in such that it reduces stress on your transmission. The rattle at idle I would say is nothing to be concerned about, the clutch disc is absorbing the vibration and it may make a little noise, and may rattle the gears a bit in neutral.
Some opt to swap the dual mass flywheel for a solid conventional flywheel out of diesel trucks and go with the conventional design w/ springs in the clutch disc for strength and reliability, yet they encounter quite a bit of resultant rattle at idle and in neutral (what you are encountering in your Viper), and need to reprogram the ECM and increase the idle up a couple hundred rpm to reduce the low end vibration / rattle (increasing the pulse frequency to reduce rattle). DMFs do not have springs in the clutch disc.
Porsche used a DMF way back to absorb these vibrations (especially with less number of cylinders = lower frequency of pulsations). DMFs don't seem to be reliable with excessive torque, the springs are designed for a specific compression rate, and the diesel guys like myself who crave more torque end up abusing the DMF springs to destruction (due to the high flywheel inertia bouncing around). Most conventional clutch designs incorporate the springs in the clutch disc to absorb this vibration. A little bit of rattle is better than a DMF.
That's what it is, and what it is.. is just an opinion.
Edit: Here's a couple pics to describe a DMF vs Conventional, not that anyone asked for this excessive babbling.. I'm just bored at the moment and my wife is at work.
This pic below is a DMF flywheel, hard to see, but it is 2 piece, the springs are inside, the DMF clutch disc below this image has no springs. The bottom image is a typical Viper clutch assembly, notice the springs in the clutch disc, and the Viper flywheel is solid as most are used to working with (not shown).
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It would be safe to suggest it has nothing to do with oil or odd firing. Don't worry about it, enjoy the V10 torque pulsations and melt your tires.
