Differential Fluid Change
Loosen Up The Cover
The Jeep Factory Service Manual maintenance schedule B recommends that you drain and refill both axles every 12,000 miles. You should also do this if you cross deep water or get stuck in deep mud. My FSM recommends Mopar® Hypoid Gear Lubricant or equivalent. It also says when equipped with TRAC-LOK, include 4 ounces of Friction Modifier Additive. I was able to find gear oil made for limited slip (TRAC-LOC is limited slip) so no need to worry about the additive.
One more advantage to having a decent amount of lift is there is plenty of room to work under my Jeep without getting out the jack stands. I use a good sized drip pan under the entire differential. And, I always test for a breeze because oils blows!
I like to loosen all of the bolts that hold the differential cover in place, removing the top and bottom bolts first and leave the middle ones for last. When I am down to the last 4 bolts in the middle, I will loosen them several turns and if I am lucky the cover will pull away from the differential. I may have to pursuade it with a rubber mallet, but I do not pry under the cover or hit with metal hammer so I don't damage the smooth sealing surfaces. Before I remove the cover completely, I will let all of the fluid drain into my drip pan.