If your rotor overspeeds, there is danger of your T/R drive shaft beeing bent. The bearing inside of the tail boom can dampen only up to a certain RRPM. Unfortunately I have no longer access to a R44 Maintenance manual where everything would be explained in detail. I think up to a certain RRPM (I believe it is if your RRPM goes into the upper red arc of your rotor tach) overspeed all that has to be done is do a T/R drive shaft runout. Obvious there are limits on how much runout there can be and if too much the drive shaft will have to be replaced. In a major RRPM overspeed (I believe this is if the RRPM exceeds the upper red arc on your rotor tach) you will have to replace the T/R drive shaft. As i remember right, there is also in a major overspeed a requirement to dye check the rotor blade spindle for cracks and the M/R bolts have to be replaced as well. In a minor engine overspeed the A&P will have to drain all engine oil and check the sump filter and the sucktion screen filter for metal (I highly recommend an oil filter system from Airwolf, but Robinson offers that as well but I have not seen one nor do I know if it is just as good). In a major engine overspeed, send your Lycoming back for overhaul
Hopefully this helps a little. The R44 is handling the rotor speed much better that the R22. The R44 gives a pilot more time to react to rotor speed climb and or decay.
Cheers,
Bitmonx