I just completed my rear differential fluid change and it only took about an hour. As always your job will be easier if you have an extra set of hands.

Here's a list of tool and things I used for the job:

1. Ramps - so that I could get under the car
2. 14mm short external hex socket- Finding a 14mm socket locally was next to impossible and the one I did find was way to long. The fill hole on the differential is right by the exhaust, which made it difficult to fit anything longer than the short 14mm hex socket. I found it in a set on ebay for about $15-$20 shipped.



3. Drain pan to catch the fluid
4. Shop towels or paper towels - to keep your area clean

Here's a pic of the mess I made:


5. Hand pump - To pump fluid into the differential
6. 1/2" clear tubing - So that you can attach to your pump(optional)
7. Gloves - to keep your hands clean (highly recommended)
7. 2 quarts of Mobil 1 75w90 synthetic gear lubrication - You only need about a 1.5 quarts. I would get an extra quart if you want to do a flush.



I put the rear of the car on ramps so that I could get under the car. Once I had the vehicle up I located the fill and drain plugs. It is recommended to remove the fill plug before opening the drain plug, that's to ensure that you don't get stuck with an empty differential that can't be filled because you couldn't get the fill plug open. The fill plug is located on the driver's side, more towards the top of the differential, close to the exhaust.





The drain plug is on the passenger side, on the side of the differential towards the bottom.



The fill and the drain plugs are on there pretty tight, but if you just work on it, they come right off. I didn't need to use a breaker bar and there really wasn't too much room to use one. Here are the plugs removed, they appear to be identical.





Since I had the rear of my car elevated, I had fluid coming out of the fill plug when I removed it. Always have a pan under the differential when you decide to remove any of the plugs and even when you are filling to catch any fluid that leaks.. I had a bit of fluid spill, but I would have caught it if I had the pan there.

The fluid I removed was pretty dark, but not as dark as motor oil when used. The new differential fluid is transparent with a gold tinge to it, so it was definitely time to replace the differential fluid. The old fluid had a slight glitter to it when placed in sun light, so I assume it was tiny metal shavings, but there were no large shavings. I removed about 1.5 quarts of fluid, more or less. Next time I do the change, I may pour some new fluid to flush out the differential, there seemed to be some old fluid left in the differential.



I cleaned up the drain plug because it had a bit of build up on it. I tightened the drain plug until I felt it was very tight and then I started to refill the differential fluid. Refilling is the most difficult part of the whole job. I tried using a clear tube attached to the tip of the differential fluid bottle and then squeezing the bottle. That didn't work because I couldn't get the bottle in the right position and the tube kept coming off of the bottle. Finally, I bought a cheap pump to pump the fluid in to the differential. The pump was still fairly difficult to use, but it worked better than squeezing the bottle. Make sure to find a good pump or you'll struggle to fill the differential. I drove the car off the ramps and squeezed under the car the best I could and continued to fill the differential until I had fluid coming out of the fill hole. Make sure to have the fill plug close so that you can install it to keep all the fluid from coming out. I probably spilled most of the fluid during the fill process, but it's a lesson learned. Tighten the fill plug and clean up everything and you're done.

This was the easiest thing to do on our car besides an oil change. The most difficult part is filling the fluid and that's it.

I was going to do the C55 differential cooling fin, but I didn't have the right tool to do the job. I had to remove three bolts on the rear of the differential, but the bolts look to be 12 point or something like that. Can anyone tell me what type of socket I need to remove those bolts?



Here are some pics of the adapter to install the C55 differential cooling fin:




There are three long bolts to attach the adapter to the rear of the differential and two shorter bolts to attach the cooling fin.


Pic of the cooling fin:

 

I figured out what type of socket I need, it's called a xzn or tripple square. I think it's a 12mm socket, but I'm not too sure.

 

good job bro, its funny 5 years ago this procedure was treated like rocket science

 

I remember when I first got the car I was scared to do an oil change myself. Now I won't let anyone do my oil change.

 

(quick thread jack) what pump do you guys use for an oil change to extract the oil. BTW, thanks for the DIY thread... it will help me in the next few months when I decide to do this.

 

I purchased a pela pro 14, holds 14.8 quarts. I think I paid $150 shipped. Probably one of the best tools I've purchased. Oil changes are a breeze now and it gets out as much oil as removing the drain plug.

 

where did u buy c55 fin adapter for c32?

 

I got it from Frankw and he got from Hong Kong. I there are only around 3-4 sets in the U.S.

 

so the fins hang down below the diff? Can you send a picture with the fins installed?

 

I haven't installed it yet because I need to buy the tool.

Here are some pics of the fin installed on frankw's car:

 

Cool!

Sorry, I didn't see that you had written earlier that you didn't have the 12-point torx tool. I found some here:
<http://paceperformance.com/i-5927138-cta8510-5pc-12-point-stubby-square-drive-bit-set-with-holder.html>