B206 Free Wheel Unit Failure
Early model JetRangers did have a chip detector in the freewheel unit housing that was wired to the system. If this chip detector activated, it illuminated the 'TRANS CHIP' light in the cockpit and it was then up to the mechanic/engineer to determine by the process of elimination which specific chip detector was shorted (mast bearing, sump, oil monitor or freewheel). Later model JetRangers retained the freewheel chip detector but it was not wired into the system - possibly a result of the historical reliability of the freewheel unit.
The practice of pilots removing, examining, cleaning and replacing magnetic plugs has long been somewhat contentious, should they or shouldn't they. As 'Ascend Charlie' says, it's not a checklist item but how can you deter a safety-conscious pilot from doing it? Those against it say it isn't necessary and the practice carries the risk of a pilot incorrectly replacing the magnetic plug resulting in a possible oil loss (yes, I know they're supposed to be self-sealing) or the magnetic tip positioned where it cannot pick-up any debris.
There is one point on which all mechanics/engineers (should) agree and that it is the highly undesirable practice of pilots cleaning magnetic plugs without notifying maintenance. It must be remembered that in addition to catching the chips/flakes/slivers of a rapid component failure, the chip detector also monitors the gradual degradation of a component by the steady build-up of sludge/paste over an extended period of time. All conscientious mechanics/engineers keep a mental note of this. Therefore it follows that if anyone is cleaning the magnetic plug on every pre-flight then this very important information is lost. So if you feel you must look at it then go ahead, but please don't clean it, and ensure you put it back correctly.