How do you change rear differential oil grizzly 660?

To change the rear differential oil on a Yamaha Grizzly 660, first ensure the ATV is on a level surface and secure it with a block. Remove the drain plug from the rear differential and allow the old oil to completely drain out. Replace the drain plug, then remove the fill plug and use a funnel to add the recommended differential oil until it reaches the fill hole. Finally, replace the fill plug and check for any leaks.