How do you change rear gear case oil in Polaris Sportsman 400 year 2003?

To change the rear gear case oil in a 2003 Polaris Sportsman 400, first ensure the ATV is on a flat surface and secure it. Remove the drain plug from the rear gear case and allow the old oil to completely drain out. Once drained, replace the drain plug, then remove the fill plug and use a suitable gear oil to fill the case until it reaches the recommended level. Finally, replace the fill plug and check for any leaks before testing the ATV.