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?

Which Diff oil should I use?

Redline 75w90NS Gear oil quarts and cases (w/o friction modifier)
or
Redline 75w90 Gear oil quarts and cases (w/friction modifier)

I think I used the 75W90 (no NS designation). Honestly, I never knew there was even a second option.

^ this question was raised on another thread as well. Don't use the NS version as it is not meant for hypoid LSD's.

Just did my diff and man was that stuff nasty! Thanks for the DIY spearfish, +1

I will be doing my rear diff change soon. Can't wait to smell the stuff!!!

No problem :). Between the transmission and the diff changes, the diff was visually more pleasing to change. The amount of junk that came out was impressive. However, I didn't notice any driving difference. The tranny however had pristine looking fluid come out, but it shifts like butter now. Go figure.

Just don't get it on your hands. It's like the acid saliva from Alien. (but not corrosive, just nasty)

was there a lot of crap on the magnetic drain plug?

i like to refer to it as the devil's piss.

Oh I will make sure to have on some gloves!

It was my first time and yes there was. Make sure you clean it throughly.

Some pics from when I changed my fluid a couple weeks ago. So you guys can see the drain and fill locations.

Sorry they're so large and some are blurry. :tiphat:

http://www.liquidc4.net/images/fluids/diffplugs.jpg

Drain Plug
http://www.liquidc4.net/images/fluids/diffdrain.jpg

Fill Plug
http://www.liquidc4.net/images/fluids/difffill.jpg
http://www.liquidc4.net/images/fluids/difffillfar.jpg

Here's what mine looked like

http://i766.photobucket.com/albums/x...lDrainBolt.jpg

http://i766.photobucket.com/albums/x...nBoltclean.jpg

Just for reference, but how often should you change your differential and transmission fluid?

Don't recall of the top of my head but it is in your service manual - its the first big service IIRC...

IIRC it's something like 30k miles, but IMO if you're really hard on the car it wouldn't hurt to do it more often.

Does anyone know the difference between Redline 75w90 and 75w90NS? The 'regular' 75w90 is what I put in the rear diff during my last change. Reading the info online says it's not for manual transmissions due to issues with the synchros...I assume it's fine for the diff. Then there is the 75w90NS which is listed under manual transmission fluids but is GL-5 which is rear diff compatible. The description for the NS also seems to talk more about LSDs and improving locking ability. (in contrast to an earlier post saying it's not hypoid gear compatible)

Thoughts?

As far as I know there is just a friction modifier added for LSDs with the NS version. Other than that they are both GL-5 fluids (which is why you don't use them in your GL-4 tranny).

Any word on the NS version of the Redline? Im about to do my interval change and thinking of leaning towards (NO NS) because our factory ones dont need friction modifier when replacing.

What is the interval for changing this?

Interval is usually 30k miles I think. Final word I got is to NOT use the NS version.

thanks Spearfish....

Just Changed My Rear Differential Oil
 

I just changed my Rear Differential Oil today with the help of this thread! My Z has 4,000 miles on it.

Thanks to SpearFish and (Jeff) Schrute for helping a brother out.

By the way, I am most likely the biggest noob when it comes to cars on this forum. I've always paid an arm and a leg to get my maintenance done on my other cars. Now it's time to do it myself and save some money! Everyone has to start somewhere.

My point is, don't feel discouraged to do this. It is very easy and if I can do it, so can you! :tup: (I changed my engine oil a couple weeks back, that was also very easy too!)

Anways...

Here's a picture of the old rear differential oil (left side) that came from my 370Z and the new RedLine 75W90 oil (right side). Looking at the difference, I am so glad that I changed the rear differential oil now than later!

Might I also suggest using a battery powered siphon pump. I bought mine from Amazon, this is the exact one I got (there are cheaper ones): I think battery powered is easier than air pump powered. It was so easy for me to pump the new oil back in with this: Amazon.com: Sierra Tools JB5684 Battery Operated Liquid Transfer Pump: Home & Garden

I hope my post helped. It's the least I can do! Thanks! :tup:

I'm lost... what is the NS version? I see two different 75W90s on Redlines site, one is the regular and one is their shockproof version. Which one do I not get?

Here is the pump I'll be using next. Easy to clean, easy to use.
fluid transfer pump

Anyone?