Remove cover/clean/fill. Note, there is no gasket. Factory and most use RTV. Scrape old off and reapply. There are gaskest available. A reusable on is I believe called "lube locker" Don't forget to do the front diff also
2003 TJ, 33" BFG AT, 2" BL, 2" BDS spring lift, Truck Lite headlights, Homemade sunrider top.