Follow these steps to replace the cover on your differential housing. These steps may also be used to replace the fluid alone. Please keep in mind this is a how to guide, not a certified repair process. I assume no liability for damage to your vehicle as a result of this instructable.
Step 1: Gather Tools and Supplies
As you begin the process of replacing the differential cover on your vehicle, you'll find its easier to have the tools you need at hand, rather than to have to climb under the vehicle multiple times because you forgot your tools. Below you'll find a list of the more commonly needed tools and supplies for the job. Your mileage may vary, as every vehicle will be different. You will need the following.
> Combo Box Wrench
> 3/8" Drive Ratchet Extension
> Razor Blade( a gasket scraper is also acceptable)
>Oil Drain Pan
>1 Can Brakleen
> Silicone Gasket Maker(Also known as RTV, some vehicles may also have a pre-made gasket to bolt on)
> Appropriate Weight and Chemistry Gear Oil
> Shop Towels
> Teflon Tape
Step 2: Drain Differential and Remove Old Bolts
Begin by placing your oil drain pan under the drain bolt. Continue by using your 3/8" drive ratchet extension and inserting it into the lowest plug on the differential. Using the lefty loosey/righty tighty rules, loosen the plug and allow the gear oil to drain into the pan. Continue on and use your ratchet with the appropriately sized socket to remove as many of the bolts as possible around the perimeter of the differential cover. Use your combo box wrench to remove bolts that may be hard to reach with the ratchet. Once the bolts have all been removed pull on the cover and it will start to separate. you may need to use your razor blade or gasket scraper to get the process started. Be very careful if you choose to use the razor.
Step 3: Clean Housing
Now that you have removed the old cover, it is time clean the sticky old fluid out. Using the Brakleen you've got handy spray the housing and gears from top to bottom. This fluid will evaporate quickly, and will not leave any residue. Once you've got the gears cleaned up you can check for signs of abnormal wear and damage.
Step 4: Scrape Old Gasket Material
Using your razor blade or gasket scraper work around the mating surface and carefully remove any old gasket material. Be careful to avoid pitting the mating surface as it can cause seal issues and could contribute to a leak.
Step 5: Install New Cover
Using the Silicone Gasket Maker (RTV) trace the outline of your differential cover making sure to apply the sealant to the inside of the bolt holes in a continuous form. Line the new cover up on the differential housing and push into place. Make sure you have a bolt in hand as you'll want to anchor the cover once you've mated it. After pressing the cover into place, hand tighten the bolt and then continue around the cover with the remaining bolts. Use your torque wrench to tighten these bolts to manufacturer's specs. Using your Teflon tape wrap your drain plug and install it into the drain hole. Make sure you torque this plug to manufacturer spec.
Step 6: Fill With New Fluid
Now that you have your new cover on and torqued appropriately it is time to fill your differential with gear oil. Follow your manufacturer guidelines for viscosity, type, and capacity. Some differential types require full synthetic, while others require conventional with a friction modifier. Be sure you get this right otherwise your performance may suffer, or you may damage the internals. Once complete use your Teflon taped fill plug to plug the fill port, and begin cleanup.
Be sure to dispose of your fluid properly based on local law and environmental concern.