It's a clutch for a polaris ranger TM (Task Master)
It rattles because at low idle (under 1200-1400) the arms flop back and forth as they go from top to bottom.
if it spins faster they "float" just below the engagement point. It only has 2 weights.
You can pop it open and put some thick grease on them to quiet it down. You can also add a tiny bit of weight to get them "floating" at a lower RPM. Drill and fit a tungsten pin in each 1.
I'd just up the idle till they quit.
http://www.partspitstop.com/oemparts...2/drive-clutch