WS ATF Question

Actually, 2004+ if you need exactness...

 

Yes, the photo is the NHW-20 (2004+) transaxle. It is essentially the same as draining and filling a manual transmission or differential. The spec for refill is 3.8 qts and that is approx. how much I needed.

 

Why not use the picture that lays it all out? from the "maint50k"
page: http://techno-fandom.org/~hobbit/cars/maint50k/nakedunder.jpg
annotated to show which plug is which. That's on an '04.
.
For pix of '01 - '03, you want this page instead. Jesse has
been running around on a load of ATF-WS, about to break 350K, and
we'll probably do another change on his car in the spring.
.
_H*

 

Bob,
I read your excellent sticky on the transaxle service where you state the same thing concerning high copper content in the Amsoil product. Is this suspected from the windings? If so there's 2 things I don't understand: Am I wrong in thinking any winding metal exposed to the fluid would be considered a short to the winding? I'm sure there would be some voltage conduction through the fluid from a compromised conformal coating resulting in a damaged high voltage supply or mg.Its the same thing as big transformers that soak in oil or liquid pcp back in the day. Any breakdown of the winding conformal insulation coating would expose a winding voltage to oil or other coolant resulting in very bad things. Same thing in our CVT case. So your base statement of copper in the fluid from windings infers raw winding exposure to fluid. I doubt that without imminent failure. The WS fluid has no unique anti-conduction properties or conformal friendly properties in fact correct me if I'm wrong but the WS was not formulated specifically for the Prius. It is also used in other Toy transmissions like the Tundra. Bob, you are obviously the Prius guru and always enjoy your posts. I look forward to the ensuing dissertation!

 

It is possible the copper came from some bushing material but I would have expected to see other bushing material in the sample:


T - Type T-IV
U_ATF - Amsoil ATF
WS - Type WS
"miles 0" - reference sample, virgin test sample

The few transaxle failures appear to have involved shorts in the stator windings that get progressively worse. The concern is a transaxle oil that gets progressively conductive in the high voltage fields may promote the first, small short that gets progressively worse. Florian Steiper has done an excellent job of failure analysis and the attached photo of his shows the one such failure.

Agreed.

This is hard to say since I'm not on the Prius engineering team. However, "Development of New-Generation Hybrid System THS II - Drastic Improvement of Power Performance and Fuel Economy," Koichiro Muta, Makoto Yamazaki and Junji Tokieda, SAE 2004-01-0064, pp. 10:

The basic construction of the transaxle, in which the electric motor is integrated, is the same as the THS. However, the losses in the drivetrain have been reduced. The main changes are the adoption of the ball bearings at the reduction gear, and low friction oil. As a result, friction loss is reduced approximately by 30% . . .
​

I can not tell if Type WS was formulated for the Prius or simply another alternative that happened along at a good time. Regardless, its properties are excellent.

Check the viscosities of Type T-IV at 53k miles and compare it to the starting viscosity of Type WS (see earlier chart.) You'll notice Type WS starts with viscosities that Type T-IV wears down to and fairly quickly:

Now my interest in viscosity comes from "Evaluation of 2004 Toyota Prius Hybrid Electric Drive System Interim Report" Ayers, Hsu, Marlino, Miller, Ott and Oland, ORNL/TM-2004/247, that included measurement of energy loss as function of transaxle oil temperature, which is a function of temperature:

I think it is more likely that the lessons learned by the Toyota transaxle team from the Prius have been shared with the other product lines. Improving the transaxle efficiency improves towing capabilities and mileage . . . a win-win.

Does that help?

Bob Wilson

 

Excellence as always Bob. Thanks very much. I always learn something every time you post. My nagging concern is if there is the slightest compromise of conformal coating will the MG 3 phase winding fail? I think yes given the voltages and current involved. It would surely not survive any 2 raw motor field windings touching each other which is what I think that picture depicts given the damage. I guess my curiosity was peaked when I have seen alot of posts here with the poster stating " Hey you have to use WS fluid ONLY because there's high voltage in there"!! That got me sitting up in my chair.Wow..we have trans fluid that doubles as high voltage transformer coolant. Yikes! I did my homework on the WS fluid. The WS fluid is nothing special. It just so happens there is electric motor windings in the gear case in our car. I think WS is more formulated to the CVT gear system than anything else. The WS fluid is a very high quality fluid that has consistent low viscosity, very shear stable with excellent low temp shift ability & API 70W/75W GL-4. Its compatible with Mercedes Benz NAG-2 & Ford Mercon SP fluid. Its an excellent trans fluid. There's better out there though. Your claim, no proof of copper in suspension is what has me typing. It would be amazing that fluid as high quality as Amsoil would attack the windings enough in that short of a time that it would eat the conformal and dissolve copper winding without resulting mg damage. My whole long winded post is can exposed windings survive in this fluid? And if so it surely wouldn't with worn out fluid metal heavy. But I really don't think so.
Anyway my car approaches 5K very quickly. Its already started flashing the maint req light at me. My contribution to your awesome efforts is to change out my WS fluid at 5k. Have it analyzed and post to contribute some baseline numbers. Thank you very much Bob.

 

Excess copper is probably from bronze bearing bushings, not
motor windings. The motor windings are enameled magnet wire,
and if you were getting copper from those it would mean the
enamel was gone and I think by then you'd know there was a
problem.
.
_H*

 

I'm not ready to rule that out either. I noticed the Amsoil preserved the starting viscosity and that would have kept the stresses high on the bushings.

The only way to really know would have been to analyze microscopic fragments and compare them to known samples of bushing and winding wire. But one thing for sure, not my transaxle.

I didn't mind trying Amsoil but only with testing to understand what is going on. The cold weather, hill roll test after the initial oil change showed significant reduction in rolling resistance. But when the oil test results started coming back with high Cu content, I lost any further interest in that product in my transaxle.

Bob Wilson

 

You may want to follow Florian's reports in Prius_Technical_Stuff. That photo is just one of several dozen including removing the wire from the failed motor. Florian speculated that his transaxle failure might have been a latent, manufacturing defect. Certainly there have been a small number of failures that we know about.

My understanding today is that when a short develops in a winding, it becomes progressive, drawing energy from the spinning rotor. No external source of power is needed thereafter. The asymmetrical load causes a noticeable vibration that as more and more of the winding chars and shorts out, the energy losses, vibration and heat gets worse and worse.

Those stator windings sure look like a reasonably high voltage set to me. In the NHW11, we're dealing with ~270 V. The NHW20 is at closer to 500 V.

Interesting. Could you elaborate on "better"?

You might want to look at 'toyota-prius-sat2' files folder, reports '284185', the sludge analysis, and '278169' the "Microscopic Analysis Report." The microscopic analysis suggests bushing wear.

Regardless of the exact pathology of Amsoil ATF, the test results caused me to stop the experiment and caution others to avoid it too. As for Type WS, I am continuing that experiment and other than the carry forward of oil that was not flushed, I'm OK with the preliminary results.

Excellent but you realize the maintenance light is mileage driven, built-in, to trigger engine oil change. The owner's manual should have a set of instructions on how to turn it off.

We have an outstanding question about the high silicon levels seen in some of the oil samples. Two causes have been suggested: (1) dirt/grit contamination and (2) case sealant. Your 5k sample from an NHW20 will help us understand a little more about the early wear patterns of Type WS in your model transaxle. I have some other areas of investigation but nothing to report, yet.

Thanks,
Bob Wilson

 

I finally did my tranny fluid change yesterday. Switched to the WS formula in the process. Unfortunately I did not save a sample for testing. Sorry!
The old fluid looked awesome though, so the previous fluid change was most certainly in the last 30K miles or so. I heard the hiss of air when I removed the fill plug, so the seal was good. The old pan gasket was still looking ok, but I bought a replacement anyway. The strainer looks great also, so I did not remove it for cleaning. The magnet did have a lot of metallic gunk around it, so that needed cleaning. I then filled up the 5 quarts through the fill hole with extended PVC tubing to the top. I will look forward to seeing a little improvement in MPG, plus the reassurance I got fresh fluid to keep my Prius going for a while longer.
Thanks to BWilson and Hobbit for the helpful info and pics for this DIY.

 

Excellent! There has been a pattern that vehicles in less dusty areas tend to have better results than those from dustier areas. Sounds like you are good to go!

Bob Wilson

 

for 20 something bucks every 60-100k miles or so, i wouldnt mind buying atf ws, its pretty easy to fill too i made this contraption with a hose and a funnel, just stick the hose in fill hole and fill it up.

 

Thanks alot Bob. Excellent as always. Very interesting about progressive winding damage. Have never heard that. That would be quite catastrophic to our trans. I plan on doing my 5K trans oil this weekend. Who do you prefer as a oil sample tester so to keep our baselines 100% accurate please. Also I have plans on using some high performance aftermarket trans oil once I have some decent baseline WS numbers for you.Thanks, Ray

 

Hi Ray,

I used these folks starting with their basic oil analysis and ask for an additional 40C/100C viscosity test, ~$20:

PdMA Corporation - Oil Analysis - Excellence in Lubricant Analysis

PdMA Corporation - electric motor testing, oil analysis

They will want your e-mail address and within a week you'll get an e-mail report of the results.

Bob Wilson

 

Thanks alot Bob. I will surely use them and post results.

 

I'm interested to see how your 5k result compares to my 10k (actually 9562) result, particularly the Si ppm.

 

I changed my trans fluid today. Thanks for all the help provided in this thread! I bought 4 quarts of the ATF WS locally and it took under 30 minutes to drain and refill. Toyota did a great job ensuring easy access to both the drain and fill plugs. The coolant drain and trans fluid drain plugs could easily be confused, however. I used a small hand pump to pump the fluid from the bottle to the filler hole.

The fluid was slightly dark, but didn't smell burnt and there was a small amount of metal on the magnet. I saved some mid-drain fluid and already sent it off to Blackstone Labs for analysis. See the stickied thread at the top of the forum regarding the trans used oil analysis for details on the oil analysis.





My Pri has 26,200 miles on it and this is its first ATF change.

 

LUV Toyota in Jamestown NY wants $140

 

I just changed my transaxle fluid in a 04 prius with 41576 miles. Do you guys still want samples?