Alright, just in case anyone was wondering how to change your rear diff fluid, here is a write up on how it's done. It's a pretty simple job, and is better (and probably cheaper) to do it yourself, rather than taking to a shop of the dealership.
***Extra Information from YBnormal07***
1/2" ratchet (breaker bar is probably better)
1 quart of rear diff fluid (75w90)
1 oil pan (at least 1 quart capacity)
Step 1: Make sure your car is on level ground, as to properly fill the differential case. There is enough room to get underneath the rear of the car without jacking it up. Put the car in gear, pull the E brake up, place an oil pan under the diff, and you're ready. You can jack the car up while loosening and tightening the plugs, just make sure that when you fill and drain the diff case, that the car is leveled.
Step 2: As you can see in the picture, there are two plugs... the top one is the fill plug, and the bottom one is the drain plug. Both of these plugs are in there pretty tight, and removing them is definitely the hardest part of the job… don’t be afraid to use force. First, you’ll want to remove the “fill plug”, to relieve pressure in the tank. Place the ½” drive of the wrench into the square indentation on the plug, and twist it out.
Step 3: Once the “fill” plug is removed, remove the “drain” plug the same way, and let the fluid drain out. There isn’t much pressure behind it, so it won’t really “splash” out or anything like that. If you want, you can put an air compressor up to the “fill” hole and blast a lot of the gunk out of the bottom of the case, but keep in mind, this is EXTREMELY messy.
Step 4: Once both plugs are removed and the oil is drained/draining, clean the surface of the two plugs. The “drain” plug has a magnet to collect any metal particles, and keep the gears safe. Make sure to clean both plugs so they look at least as good as the ones in the picture. When cleaning the plugs, look for any metal shavings. Small shavings here and there are normal, but if you find any pieces more than a few mm across, it could be a sign that your differential is shot, and you should have it looked at. Also, make sure to clean the threads of each plug and plug hole to get rid of more grime and ensure that it seals the hole properly.
Step 5: Once the oil is finished draining and the plugs are cleaned, replace the drain plug, leaving the fill hole open. Take the differential fluid and pour (or squeeze) it into the fill hole until oil starts to leak out. The case only takes .8 quarts, so you should have some leftover fluid. To make things easier, you can buy a siphon hand pump, allowing you to pump the oil into the case, which is much easier than trying to squeeze it in, as space is quite limited.
Step 6: When the case is filled, put the fill plug back into the hole, make sure both the drain and fill plugs are tight, and you’re done. It is extremely important not to over torque these plugs! Best bet is to measure the force to break them loose with a torque wrench, and apply that same force to tighten them back up.