Once again, if you’re not comfy with crawling under your car don’t do this.
For this little adventure you’ll require the following tools.
1) A way to raise the rear of the vehicle.
2) A 10mm allen wrench or allen socket. (socket is better).
3) A large syringe for filling the diff.
4) 2qts. of GL-5 Fluid, once again I used Royal Purple Max Gear 75w90.
Step 1) Raise the rear of your car. This job will require that you keep it up and level.
Step 2) Remove the fill plug using the 10mm allen socket. It is located on the passenger side just behind the rear CV Joint. Always do this first, if you can’t open the fill plug don’t pull the drain plug.
Step 3) Place a drain pan under the drain plug and drain the rear diff. After all the nasty fluid is out replace the plug and torque to 26 lb-ft.
Step 4) Make sure the car is level then using the syringe, put 1.75 quarts of fluid back into the rear diff. Then slowly add until you see fluid dribble out of the fill hole. Mine took just under 2 quarts. The manual says 1.9 quarts which I guess is right. Replace the fill plug and torque to 26 lb-ft. Lower your car and feel secure in the knowledge that your rear end is well cared for.
(Original: http://www.audiworld.com/tech/misc33.shtml) – By Ron Curry