Changing the rear differential oil in your Jeep is a very important part of the maintenance schedule' interval service. As does any type of petroleum-based lubricant, the oil breaks down after wear and tear and time, thus losing important chemical properties to maintain its intended purpose. The fluid will also begin to fill up with small metal filings from the friction on the rear gears. Changing it per recommended schedule intervals will help prevent premature wear to the rear differential gears.
Drive the front of the Jeep up onto car ramps and then apply the parking brake.
Lift the rear axle of the Jeep with a hydraulic jack and then support the rear axle onto jack stands. Position the jack stands so they are a little lower than the front ramps. This will angle the Jeep down in the rear and help the fluid drain from the rear differential better.
Place a large drain pan underneath the rear differential cover and then remove the fill plug. There are two types of plugs used on Jeep differential covers. One requires the square drive of a 3/8-inch ratchet and the other employs a rubber plug in the cover that can be pried off with a slotted screwdriver. Remove the plug applicable to the Jeep.
Remove all but the very top differential bolts with the ratchet and suitable socket. Loosen the top bolt so it's about half-way removed. This will hold the cover once the gasket seal is broken free.
Use a hammer and flat chisel to separate the cover from the mating surface of the differential. Start at the bottom and work your way up each side. Be aware that when the cover breaks free, the differential oil will pour out. Make sure the alignment of your drain pan is ready to catch it properly and you're not in the path of the fluid.
Allow the differential fluid to drain thoroughly. This will take some time, but the more fluid to drain, the better. Once the fluid is a mere trickle or completely drained, remove the remaining top cover bolt and set the cover aside.
Use brake cleaner spray to clean the rear gears inside the differential. Be thorough and use a copious amount of spray. Again, allow the brake cleaner fluid time to drain from the differential. It will not take nearly as long as the gear oil did.
Tuck a large, clean shop rag around the rear differential gears to prevent contamination.
Spray the inside of the differential cover with brake cleaner and wipe clean with a different shop rag.
Use a die grinder with medium reconditioning discs to clean off the old perma-gasket from the mating surfaces of the differential and the differential cover. Be very thorough. Any remaining gasket left behind can lead to a potential rear-end fluid leak.
Remove the rear rag covering the gears and use it to remove any gasket that has blow into the differential. Spray brake clean in again to clean out any reconditioning disc particles.
Apply 1/4-inch bead of RTV gasket sealant to the differential cover. Be sure to apply the bead in the center of the mating surface and to angle the bead on the inside of the bolt holes. Getting too close to the inner edge of the cover can allow the liquid gasket compound to contaminate the rear differential oil. Take your time and be thorough.
Allow the RTV gasket sealant time to cure. Refer to the directions on the tube before applying to the differential. Once enough time has passed (according to the directions on the tube or packaging), carefully replace the cover onto the differential. Replace the bolts and tighten in a crisscross fashion using a torque wrench set to 30-foot pounds and a socket.
Allow more curing time for the RTV gasket sealant if directed to before adding the gear oil. In the interim, lower the Jeep to the ground so it's level.
Add the gear oil into the fill hole of the differential cover until it seeps slightly from the fill hole. Use a hand pump if necessary to pump the gear oil into the fill hole and then when it begins to seep slightly from the hole, replace the plug in the same manner you removed it.
