Axle oil change.
The best way to change differential fluid is to pull the cover.
Most oil change companies suck the old differential lube out through the filler plug. This changes the lube but does nothing to remove the harmful sludge that has accumulated on the bottom of the differential housing. Once the new lube and sludge mix, your oil is filthy again.
If you pull the cover you will be able to wipe out metallic sludge out with a rag. The sludge is made up of metal shavings and metallic flakes created by differential parts wear. Some of them can be very sharp. The edges of the ring and pinion gears can also be very sharp on the edges and cut up our hands, be careful, wear gloves. Solvents work well, but if it is not completely removed, it can mix with the new gear lube and break it down.
Now is a good time to inspect the parts inside the differential. Look over the ring and pinion, there should be no missing teeth, chips or deep gouges. The gears should not be to shiny and polished but a dull silver gray with small machine marks present.
The same it true for the side and spiders inside the carrier. You will be able to see the side and spiders clearly on an open differential. Look for the same marks described for the ring and pinion. Side and spiders that have excessive wear can be replaced without completely disassembling the axle. Track-loc carries are similar, but have clutch packs behind the side gears. These cannot be easily replaced, a job best left to a professional.
When you finish the job, clean all the old gasket material from the housing and cover. Install a new gasket or apply RTV silicone and tighten down the cover. If you use RTV, give it time to cure before filling the differentialÂ with oil.