ATF fluid changes ARE Required.

experimentation

 

^ There are two points of contention: the fluid to use, and when to change. I don't see why one screw up deserves another. I change it, more frequently, but don't see your leap of logic that this justifies using unspec'd. fluid. But, it's your car, LOL.

And FWIW, the Toyota stuff cost me $9.32 a liter. The time before I bought Honda auto transmission fluid it was close to $20 per liter.

 

Agreed. This is how much I had left in my 5th qt.



However, as mentioned earlier, the fluid does expand when it warms up, so up to 10mm under the fill hole is acceptable. As for how one would measure their fluid level to be 10mm under the fill hole - that is simply beyond me.



iPhone ?

 

Bill that looks much better and was worth the early change. Seems like alot of aluminum wear. They must have used more aluminum in the gear set metallurgical formula & running gear to save weight. Anything to improve gas mileage!

And you can see with the pretty new WS fluid the pack that's on board. Alot of Calcium & Boron for TAN mitigation and that's about it.

Use Redline D4 next time and change it at 25,000 miles. Redline now specs D4 for the Gen II and I think its the same for your 3. I'm almost due for my 25,000 change on my 07 and will have that tested and will post it. Should show the same excellent wear numbers as my last 25,000 sample.

Good job!

 

You are right about it not being in a transmission gears metallurgical recipe except maybe in trace amounts in some strange alloy that would have no effect on density.

You wouldn't see it in automotive transmission gears, but, there is dissimilar metal welding and it is getting into some automotive applications. The forms I am somewhat familiar with (I had it done about 20 years ago but never did it myself) are forms of friction welding, often called inertia welding because inertia is often used to generate the friction.
It's an interesting process
Friction welding - Wikipedia, the free encyclopedia

Once the tooling is setup it's relatively inexpensive so I wouldn't be too surprised to see it in automotive sub-frames. It would be a good way to add some hard points to an aluminum structure.

 

Nitriding - Wikipedia, the free encyclopedia

 

The was in response to

which is still

Nitriding is a surface hardening process that has nothing to do with that. The gears are still a steel alloy without a significant amount (~0%) of aluminum.

 

Good data. So let's look at these between 112k miles and 420 miles:

	Column 1
0	[th]Fe[th]Si[th]Al
1	[tr][td2]14%[td2]17%[td]22%

Source: Marked Prius oil 5-1-13.pdf

Earlier tests on virgin Type WS have shown there is no Fe, Si, or Al. So these metrics give a clue as to the carry forward . . . the dilution of the virgin oil by the oil that can not be drained. Interesting how the specific atomic weights seem proportional to the carry forward. It suggests the lighter material will tend to layer on top and denser on the bottom of the transaxle sludge.

Our first drain and sample at 5,000 mi showed metalic and sealant particles. By draining early, we cut down how many times these debris particles passed through gears to be crushed to powder. The 112K and 420 mi samples gives a clue as to how bad it can get. You'll notice the larger particle population is rapidly going down.

The V100 (viscosity at 100C?) shows a pattern I had not seen before in the earlier Prius, a viscosity increase. I suspect this may be a by-product of the particle load but it has me scratching my head . . . and a little curious.

Our NHW11 and NHW20 samples have shown a history of decreasing viscosity, a 'shear down'. But here we are seeing evidence of increased viscosity. It would help if we had the virgin, Mobil ATF viscosity at 100C to determine if the "7.0" is an increase or decrease.

I remain confident that one of the best things we can do with our new Prius is to change the transaxle oil with the first engine oil change, at 5,000 miles. The second should probably be sooner rather than later. My viscosity trend suggests 15,000 service miles or around 20,000 miles. Thereafter, longer change intervals make sense but I don't have metrics suggesting the period.

I am seeing some cold-soak behavior in my wife's ZVW30 suggesting the low temperature viscosity may have increased. The first-trip of the day, loss of speed in "N" seems higher than I remember after our second transaxle oil change. Fortunately, I have the oil needed for the next change and just waiting on a weekend to make it happen and send the sample off. Before I do, I'll try to record some metrics with our miniVCI to document before and after behavior.

Bob Wilson

 

Toyota claim that the fluid in the transmission is good for the life of the car. I think there is some hysteria here regarding the necessity of changing the ATF fluid. Has any one noticed a large rash of failing Prius transmissions lately? If anything the Prius tops most reliability surveys.

If you feel better changing your fluid do it but it probably won't make much difference to the reliability of your car.
Don't put anything but Toyota's fluid in there as it is specially formulated for compatibility with your electric motors.

 

You have almost made the connection, you will not see transmission failures, there is (almost) nothing to fail, you will see shorted M/Gs, from metals moving in the ATF.

 

OK I'll play your game. Has there been a plague of shorted M/Gs?

 

When Toyota claims an early transaxle change voids their warranty, I'll be willing to consider not changing the oil. But my first NHW11 change at 53,000 mi. after the car had spent 49,000 mi. with the former owner in a hot and dusty state, Texas, notorious for high-speed driving. The plastic head light covers were already 'frosted' from the dust and dirt. Similar to what cars from the Australian interior are likely to see. But my first change was part of a cold-weather study: 2003 Prius - Cold Weather and Transaxle

Fair enough as I know there is some:


NHW11 transaxle:

The transaxle failures occur AFTER the warranty expires during which time the cruddy oil does its damage.

Bob Wilson

 

You may note that transaxle failure is the first repair mentioned.
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This gentleman thinks the suspended solids block fluid flow and overheat the insulation, leading to M/G failure
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