RageRacerM

Mileage: 50,000

Recently changed out the rear differential fluid of my vehicle. The fluid sample is just sitting in a plastic container until my Blackstone Oil Analysis kit gets here. Wish they sent me a tracking number, feel like Ive been waiting for it for a bit too long. Color doesnt mean too much (IMO), so I wont make a comment on it. Lets see what science says.

Onto transmission fluid... yea yea, no one can ever agree to this... so bringing this up is most likely pointless. Anywho, currently debating on a fluid drain and fill, not a flush. What exactly is the OEM fluid? Toyota World ATF? or will using Mobil 1 be fine?

I plan on keeping this vehicle for some time, so this matters to me.

JNP1227

iTrader: (1)

I would use OEM Fluid, thinking of doing the same planning to keep this car for 150k+ so would be worth it in my opinion.

Sasnuke

I would agree with you that the color of the diff. oil doesn't mean much, but combine that with the odor, and even the feel, and you can tell if the fluid was done or not...meaning that it needed to be changed.
Gear oil already has on unpleasant odor to it, but fluid that is no longer effective will have a rankness to it.
I don't think that's the case with your vehicle, but changing it every 50K kms (whatever that is in miles) isn't a bad idea, won't break the bank, and gives you peace of mind for the long haul.

As for the tranny fluid, I've probably read a handful of threads on here about thoughts on the fluid.
The OEM fluid is Toyota WS (World Standard) fluid.
There will be some that will say the fluid is garbage and there are better fluids out there...based on Blackstone results and a bunch of Youtube videos.
And that's fine, everyone is entitled to their opinion, or even their own Blackstone results...however...consider that all our vehicles, if you haven't change the fluid to something else, are running around the world and no one has had a tranny explode.
Now consider that every Toyota made in the last 15+ years is using WS fluid, and running around the planet, and there hasn't been a global rash of tranny's blowing up...I think we can safely say it's probably not the best, but it does pretty good.
And like with everything, it's a rabbit hole of "this fluid is better than WS", and "this fluid is better than that fluid that is better than WS", and so on, and so on, and so on.......I think you get the point.

So, after all that, a regimen of drain/fills over the course of a few years will certainly help sustain the tranny well into the future...i.e. do a drain/fill now, again a year from now, and one last time a year after that.
While this will not give you a complete exchange of fluid, there will be enough new fluid in there that the tranny can be left alone for 4-5 years after that...at which point your IS would be about 14 years old (give or take)

Noeh

iTrader: (3)

I would stick with Toyota fluids as well, Toyota is in the best position to engineer their fluids to spec to minimize problems. Harder to do as an aftermarket company engineering fluids for different car brands.

On the refill method, I read somewhere that there is a way to exchange the fluid through a cooling line. Not sure about the details, maybe ask your dealer to confirm.

HOMER350

I've exhausted the topic too ha.

I preferred OEM fluid but when my trusted mechanic said he wanted to use his synthetic whatever-it-was I had no complaints.

ABGLexus

What is rear differential fluid and how often should it be changed? This is first vehicle I've owned that I've ever even heard of that term.

jennypenny

every 4 years or 50,000 miles for rear differential

Sasnuke

I don't think there is a set interval...by just my opinion...every 2 years or 50K kms (roughly 30K miles)...pretty much the same interval as brake fluid, so you can do both in one trip, along with your engine oil/filter change.
And don't forget the front diff. if you have an AWD.

The rear differential is used to transfer the power from the transmission to the rear wheels.
It uses fluid as splash lubrication in the diff. to keep everything cool and lubricated.
The oil is thicker than engine oil and has an almost honey like appearance.
I forget the exact rating for 3IS, but usually rear diff. oil is 75W90 or 85W90...or there's about.

E46CT

Technically, Toyota WS or equivalent (there's a lot out there) should be fine. Nothing will blow up. But Toyota WS isn't that costly and there's no reason not to go for it.

As far as transmission fluid, there should be no debate. I've said this very strongly on BMW forums as well for over 10 years. Replace all the fluids, all the time, always. That's my motto whenever a "should i replace xx lubricating fluid" question comes up.

Entropy or second law of thermodynamics. There's no getting around science. All fluids break down. I assure you if you clipped a transmission line and the fluid leaked out, and you took it to the dealer to repair the line, the dealer isn't going to go running around looking for some lovely used transmission fluid to pour back into your transmission. They're going to put new stuff in.

Part of the problem is people have been throwing around the word "flush" for decades which makes people think of something violent like flushing a toilet or something else.

The idea of fluid replacement is letting the transmission discard fluid in its exit line and return new fluid to the return line until the fluid replacement is complete. Nothing more, nothing less.

EZZ

The challenge is actually finding someone who can do it right. Such a pain in the a$$. The dealers in the area wouldn't touch it.

JNP1227

iTrader: (1)

I watched a video of someone doing it on the GS350 .It actually looks pretty straight forward. Just need to know to put the same amount back in.

Correct me if i am wrong-

1. Loosen Plug bolt
2. Drain Fluid
3. Drain whats left in Overflow
4. Refill Fluid
5. Let car run to temp, drain Overflow

RageRacerM

I'll find Toyota WS this weekend and hope to be able to do at least 2 drain and fills some time next week. Will also shoot an email to Blackstone to see where my kit is.

RageRacerM

Blackstone Analysis put on hold. Recently discovered the shortcomings of Blackstone Labs.... sad...

TBD....

Flash5

What do you mean? I haven't heard anything.