I have a 2006 6mt g35 coupe with about 63k on it, today i did a list of things on the 60K service list and decided to do diy on the rear differential change. I hope this is somewhat helpful to someone.

What you will need:
2 quarts of 80w-90 gear oil (not synthetic, just plain gear oil) You will not need the whole 2 but mine took like 1.5, i just filled it up til a little ran out the top.
Fluid pump.
10mm hex bit to loosen drain plug and fill plug
3/8 drive ratchet and small extension


make sure you have your front wheels higher than than the rear to make sure all the gear oil possible can get out.

FIRST LOOSEN YOUR FILL PLUG TO MAKE SURE YOU DONT DRAIN YOUR FLUID AND NOT BE ABLE TO GET THE FILL PLUG OUT Then you loosen your drain plug, the bottom one and once it is loose make sure you have a catch pan or bucket that can hold at least 4 quarts of fluid. Once you brake the bolt loose you will need to unscrew it the rest of the way by hand to make sure you don't drop it in your bucket! Once the plug is out and the fluid is draining take a min to look at your plug, it should be a magnetic one and just look to see if there is any metal shavings on it. If there is have it checked. It will take a good 10 15 mins for all the fluid to drain out.

Replace your drain plug back and make sure is tightened down real good, some replace the washer i did not do so. I also took some brake cleaner and cleaned up around the drain plug so i could watch to see if there were any leaks while filling the case back up. Let your front wheels back down to where the car is level for the next step. This will insure you are putting the correct amount of gear oil back.

Remove your fill plug located to the right and above the drain plug. Use your fluid pump to start pumping your 80w-90 gear oil back into the differential. Some say it holds 3 quarts, mine was just a little less. I was told by the service department to fill it up until it starts to slightly drain out the fill plug hole. Once that's done, replace your fill plug and clean the area with brake cleaner again. With my car on jack stands i started my car, put it in first gear and let it run for a couple of mins while i watched leaks, and listened for anything out of the ordinary.

Hope this helps guys and sorry no pictures i couldn't get the damn things to load right.

 

Is it necessary to use the pump??

 

Yea I found it is a lot easier if you do. I mean once you get under the car you will seewhat I'm talking about. But if you finds different way let us know.

 

I used Royal Purple and the bottles were able to accept a piece of tubing. My brother was under the car holding the one end inside the diff and I was outside holding the bottle upside down. When he yelled stop I turned the bottle rightside up.

But I agree. A pump would be easier if you were by yourself.

 

Good writeup -- couple of tips: You actually only need 2 quarts since the diff holds about 1.5. The other is to at least loosen that top plug before you drain the oil from the bottom. If you drain first, then can't get the top one out, you're gonna have an interesting time 'pushing' the new fluid up through the drain hole!

And yeah, the pump helps a ton.

 

Your right about the fluid the damn dealership told me "about" 3 quarts. Ha! But about my plugs I pulled the bottom one first and not sure what you mean about not being able to loosen the fill plug?

 

Oh ok I see what you mean. Atleast check it to make sure it will break loose. I didn't even think about that so very good point.

 

Who sells Royal Purple? What are your opinions of it?

 

 

I think I found a good deal at the time at www.americanmuscle.com. But you can find it other places. Some local auto stores carry it and I've even seen it on a walmart shelf once or twice.

Like most oils, everyone has an opinion on what is the best/worst. I'll just say I haven't had any problems.

 

Swivel hips is 100% correct always loosen the fill plug first before the drain. If you drain your fluid and the fill plug is seized, you are phucked. If the fill plug is seized and you realize before you drain your diff fluid you can at least drive the car to a mechanic shop to have them work on it.



Also why not synthetic


It is not always required, I use Motul and it has a nipple that folds out of the bottle and that allows it to be poured/squeezed into the diff or the tranny.

 

good to know... I will be doing this on Wednesday!

 

I just did this a few days ago. It only took about 1.5qts. I also didn't have a pump so I had to use a funnel with a tube...only problem was the tube was a little short so I had to improvise a little bit and take the passenger side rear wheel off. Was a big pain but it was eventually done. If you do do it with a tube, pour slowly, as it is very thick, it'll end up coming back out.

 

There a thread on here "DIY for manual transmission fluid/clutch change"..for those who wants to see similar pics relating to same methods for fluid change.

 

nice write up..just changed my diff fluid tonight..what a waste of time and money !! it still looked brand new with 66k miles!! coulda lasted another 30-40k miles ! Oh well atleast i have peace of mind. Next will be the tranny fluid =)