2002 Yamaha YFM660 Grizzly factory service and repair manual, Page 125Get this manual
CHECKING THE FINAL GEAR OIL LEVEL CHANGING THE FINAL GEAR OIL
CHECKING THE FINAL GEAR OIL LEVEL 1.Place the machine on level place2.Loosen: Oil check bolt NOTE: Loosen the slightlyDo not remove the bolt, otherwise the gear oil may come out3.Check: Check that gear oil seeps out from where the check bolt was loosenedIf no gear oil seeps out, change the final gear oilRefer to "CHANGING THE FINAL GEAR OIL"