DIY: Rear Differential Oil Change
 

Well, this is a pseudo-DIY. I didn't take pictures solely because it's entirely straight forward. Here are the steps and part numbers for the things you'll need.

Required items:
Jack and jack stands
Torque wrench
10mm Allen head ratchet attachment
Nissan metal gasket x 2 (38351B) WASHER - 370Z (Z34) 2009+ :: Nissan Parts, NISMO and Nissan Accessories - Courtesyparts.com
Siphon pump (available at Autozone for $10)
GL-5 gear oil, 2 quarts (I used Redline 75W90 synthetic)
Oil collection pan or container (Autozone $10)

Instructions:

1. Jack up the rear of the car and place it on jack stands. I just used the rails where the manual says to place the jack. The metal lip is strong enough to withstand a jack and jack stands that don't have the special grooved attachments.

2. Allow the car to cool so you don't burn yourself when you drain the oil. Place the oil collection pan under the rear differential and locate the drain screw that faces towards the back of the car at the base of the diff as well as the filler screw on the passenger side of the diff. (See Image 1 in the service manual clipping)

3. Using your torque wrench and 10mm Allen head ratchet attachment, loosen the filler bolt first. This will ensure that you can get this screw open to refill the differential BEFORE you empty out the oil (you don't want an empty diff and a stuck filler screw). Once you've ensured you can loosen the filler screw, go ahead and remove the drain screw. I found an articulating joint was helpful to make the ratchet wrench fit better. I broke it loose with the ratchet and then loosened it the rest of the way with the allen attachment by hand to make sure I didn't drop the screw into my oil collection drum.

4. Allow the gear oil to empty completely...give it 10 minutes or so. You'll see it's pretty darn nasty and black. The drain screw is magnetic and you'll likely find a bunch of sludge on it that you can clean off during this time. It's amazing what accumulated in just 3,700mi.

5. Once the oil is drained, place a new metal gasket on the drain screw and screw it back in place. The recommended torque is 25-26 ft-lbs (1 ft-lb makes no difference and is probably less than the precision of the average torque wrench).

6. Next remove the filler screw on the passenger side of the differential (you may have done this already in Step 3). This will give you access for the siphon pump hose. Insert the outlet end of the siphon pump into the differential a few inches so it stays in place.

7. Place the inlet hose of the siphon pump into your fresh container of oil. Start pumping...you'll notice it takes a bit of work to pump the viscous oil up into the differential. While the diff only takes 3 pints (1.5 qts), I pumped a full 2 quarts into the diff and just let the excess run back out and into the oil pan below the car. This ensures that you have the diff filled and accounts for the oil that remains in the pump and tubing.

8. Once the diff is overflowing, you're all set. Remove the siphon hose from the diff and place a new metal gasket on the filler screw. Replace the filler screw and torque it to 25-26 ft-lbs.

9. Clean up the mess and check for leaks.

You've just changed your rear differential oil! Feel free to give a rep point if you found this helpful :)

Transmission oil change DIY coming in the next week or two (process should be very similar)

nice writeup :tup:

I hope AK puts in a Maintenance and Repair Section for exactlty this kind of stuff...

+1

Good write up. one recommendation for point #8 is that you should make sure that before plugging the fill hole, any excess overflow completely drains out. The fluid level should be exactly level with the bottom of the fill.

Also, since you used jack stands on the rear, not sure how level your car was. One way to avoid over/underfilling is to take measure the oil drained out and put the same amount back in. Take into consideration that about 0.1 quart may have stuck to the catch container.

There was certainly some tilt to the car but measuring the exact amount you put in will be darn near impossible. The siphon pump and tubing contain an unknown volume of oil, and there is no way to know how much you've cleared from the pump and tubing or how much is still contained within.

While the car was on the rear jack stands, I first took out the fill screw. No oil came out. Then I pulled the drain screw, drained the diff, replugged it, and refilled it. If anything there may be a bit more oil in the diff than when I started. One could always drop the car back to the ground, wiggle underneath and crack the fill screw to see if you drain any excess off.

I don't plan on doing that unless someone can convince me that 100ml too much oil in the diff will cause a problem. I've just driven 100 miles since the oil change and the diff is still working :)

***Just did some lurking in other forums. Looks like overfilling a diff can lead to oil leakage from the axle seals. It's usually solved by just emptying some oil out. However, people claim that jack angle won't allow you to severely overfill a diff. Mostly people have overfilling issues if they fill their diff while it's on their workbench and then reinstall it.

My addendum to this in step 3 would be to ALWAYS do this first or at least make sure you can loosen it.! Reason being is if you can't get the fill plug out for whatever reason, and you've already drained the fluid you're sorta up a creek!

Yep, I did just that but didn't put it in my original procedure description...you certainly don't want to have an empty diff and no way to refill it. That being said, it didn't take much force to break either screw loose initially. Original post updated to include this helpful tidbit.

Was there are any difference either sound or performance wise from changing the diff oil?

IMO, I doubt you can feel a difference. But in some cases it can make the diff quieter.

One other thing that should be added to the required tools list: a clothespin or tissues to plug up your nose. Diff fluid smells awful!!

Yep, the fluid smells gnarley. I didn't notice any performance or sound difference. It's more peace of mind knowing you got the nasty factory fill out. I'll be doing the transmission oil this week which I expect will give a noticeable difference.

Can you do a DIY for that one too? :tiphat:

Sure

hey spearfish, if you don't mind can you post a pic of this siphon pump? and Thanks for the writeup! +1:tup:

Here's a link. I used the exact one in the picture and bought it at Pepboys for $12.

K-Tool International (KTI72250) Mult Use Siphon Pump - KTI72250

Another helpful DIY from Spearfish - Thanks man! Made it easy! Rep added.

The tip about the articulating joint for the wrench was spot on, I was glad I had one. Also, haven't used the latex gloves as much lately when working on the car but your suggestion to use them was also a good one - this stuff kinda stinks.

edit: My journal has a pic of how much junk that magnetic drain bolt had on it. It was a lot.

I'm assuming in the LSD there is special LSD fluid in the pumpkin and when you change the oil in the diff you are just changing the "normal" oil so there is no need to use an LSD additive?