# R51 Rear Differential Oil



## LittleStevie (Sep 27, 2006)

Has anyone checked or replaced their rear differential oil on an '05-'07 Pathfinder? I have an '05, but I'm referring to the '06 service manual where it says (in bold red font) to not reuse the gaskets for the fill or drain plugs. On asking my Nissan parts dept. for the gaskets, they replied that there are none, that you just use RTV silicone on the outside of the plug. I'm going to ask them again tomorrow (hoping that someone else is behind the counter), but does anyone know if there really are gaskets to replace?

I'm considering going to 75W-90 Royal Purple MaxGear. It's synthetic GL-5 spec, as called for in the manual, and I've heard great things about Royal Purple products. Any thoughts?


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## LittleStevie (Sep 27, 2006)

Update on the drain plug gasket question - Nissan parts dept. again confirmed that there is no gasket on the fill or drain plugs, you just use silicone on the exterior after tightening the plug. They seemed to think that the gasket that the service manual is referring to is for the differential cover, which you obviously do not have to remove to change the fluid.

Just to make it easier on anyone else, I found by trial and error that the drain and fill plugs are 10mm hex. Couldn't find this anywhere in the manual, and Nissan parts couldn't tell me either, so had to do trial and error at the local auto parts store.

Now here's where I really hate to admit how much of geek I am. Just ordered an infrared thermometer (with adjustable emissivity) to see if going to Royal Purple has any effect on my differential temperature, as they claim it does. I'll probably change the gear oil on one of the next couple of weekends, after I get a few good reads on temperature with the stock gear lube.


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## LittleStevie (Sep 27, 2006)

More info on the plug gaskets. I found them on the exploded parts diagram in the service manual and went back to Nissan parts and insisted that they were there. Sure enough, they found them and had to special order them.

I drained the RFD oil this morning, and I was fully expecting to see it come out slightly amber or clear. Not so. I was really surprised at how dark and dirty the oil seemed to be, considering it doesn't see anywhere near the heat that an engine oil does. The drain plug is magnetic, and it had collected a good amount of metallic particles/shavings. But there was also a thick, grease-like substance all over the inside and end of the plug...not something that I would expect inside the differential. Not sure if it was a grease or "Neverseez" compound or something else.

So Royal Purple MaxGear 75W-90 went in, and I'm hoping that it holds up better than the stock fluid. I'll report back if it has any noticeable effect on temperatures. Based on the condition of the oil coming out of the RFD, I've made up my mind to drain and replace every 30k miles, even though the service manual says you don't need to. Just for reference, I have 28k miles on the truck, don't tow anything, and really don't push my Pathfinder too hard.


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## BMXPath (May 19, 2007)

Any updates Stevie? What are your test results? 
I am thinking about changing the diff fluid in my '05. I certainly want to use synthetic.


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## LittleStevie (Sep 27, 2006)

No apparent decrease in running temp on the rear diff with Royal Purple, so I don't have much to report. Both with the old gear lube and the new I run about 125 F on the back casing of the differential, according to my IR non-contact thermometer, after about a 22 mile trip home from work. I haven't drained the fluid since then, so I can't report on the condition. 

If you haven't done your '05 yet, definitely do it. The amount of crap that was in mine easily justified it. I'll probably change mine after about another year, and hopefully it'll look better than the factory fill did, albeit with a purple tinge!


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## BMXPath (May 19, 2007)

Thanks for the update!

I definately need to get mine done. I have about 50K on my '05. I got it with 16K and havent had it serviced sine I have owned it.

Interesting note... I have called 2 Nissan dealers to see what they charge and they both told me that synthetic is used for the diff.


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## LittleStevie (Sep 27, 2006)

Yeah, you have to use synthetic that meets the GL-5 spec. It's not worth messing around with, put in good stuff. I think I paid about $10 a quart for the Royal Purple MaxGear, and I think Mobil 1 is about the same.


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## mann777 (Jul 15, 2006)

*Makes a great difference*

Hi guys i just did mine and there is amazing ride difference .Just completed 70.
Keep a check guys on yours if u havent.


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