Transaxle Oil Analysis

Thats what she said

 

Regarding your first paragraph, the car had been driven for a good 1/2 hour - 45 mins. prior to my removal of the drain plug. I would say I removed the drain plug no more than 10 minutes from the time the engine shut off, so the fluid was pretty darn hot too.

I'm not saying there was a "higher" pressure inside the transaxle, well, I suppose technically, by definition, anything greater than a specific value of negative IS higher. I'm not exactly a fluid dynamics major, but, if you have a situation where there's some amount of negative pressure, fluid, and a drain hole involved, if air were to suddenly rush in, I would imagine the fluid would need to be displaced to some degree, or at least disturbed? I mean, after all, I did hear, for a brief moment, a "hissing" noise.

I just know that's the way it happened. No fluid appears to be seeping out anywhere externally.

I think I just happened to loosen the drain plug a bit too quick, such that gravity, and that little bit of negative pressure did their work spectacularly well.

 

Thanks for the update. I was just wondering what the used fluid looked like and how many miles you had on it.

 

Uh OH!

The cool shop air entered the hot transaxle and helped cool things off by 'expanding'. It then jetted the remaining oil out and shot the drain plug. Amazing, I hadn't considered changing the oil while the transaxle is hot:




This is the type of experiment that Mythbusters might enjoy ... with proper, hot oil resistant clothing and head gear.

Bob Wilson

 

:rockon:

Edit, hey, wait a minute, then why doesn't this really happen with the oil? I guess there's more "space" and less of a vacuum???

 

Uh, well, I WAS hoping to get a sample... It appeared black. Maybe it was sooo deep red it appeared black? I don't know, but it looked, to me anyways, no different than used motor oil. Of course, my garage lighting isn't that great, and it was at night... Car has about 87,000 miles on it.

 

2006 Prius 65K transaxle oil analysis high in iron and aluminum and silicon. Report is attached. Based on this, the transaxle oil may not be good to 120K miles as suggested by Toyota.

 

2006 Prius 65K transaxle oil analysis high in iron and aluminum and silicon. Report is attached. Based on this, the transaxle oil may not be good to 120K miles as suggested by Toyota. Attached file is in jpeg format.

 

2006 Prius 65K transaxle oil analysis high in iron and aluminum and silicon. Based on this, the transaxle oil may not be good to 120K miles as suggested by Toyota. Blackstone Oil report highlights below:

"Aluminum and iron were on the high side in this sample, but neigher were high enough to suggest any serious mechanical problems are developing in this Prius transaxle. Universal averages show typical wear from this type of system after about 29,000 miles use on this oil. If this oil was run longer, that likely explains the higher wear. The oil was normal in viscoisty for an ATF, though insolubles were at the limits. This along with the higher wear is a good sign that the oil should be changed out if you haven't done so already. Theck back in 25,000-30,000 miles to monitor."

Aluminum 101 (universal ave 60)
Iron 219 (universal ave 155)
Silicon 188 (universal ave 173

All other parameter at or lower than univeral averages.

Sorry about the multiple postings, I was unable to upload a legible pdf or jpeg file.

 

I've attached a copy of my 2004's used transaxle fluid analysis, taken at 32,755 miles back in July 2007.

Al: 79 ppm
Fe: 205 ppm
Si: 198 ppm

Note fluid viscosity at 100 degrees C was 4.7 cSt compared to new fluid at 5.5 cSt, a 15% decline. Bob Wilson previously had new ATF WS fluid tested and made those results available.

Based upon these results, I decided it was a good idea to change my transaxle fluid at 30K mile intervals in the future.

 

Blackstone's analysis of factory-fill transaxle fluid at 20,000 miles:

Al: 47
Fe: 145
Si: 201
Insolubles % 0.2
Viscosity (cSt)@100C: 4.92

"The ATF from this transaxle is the original factory-fill and that is why there is so much silicon and insolubles present. The silicon is from sand-casted parts, lubricants and sealers that were used at the factory, while insolubles are an accumulation of oil oxidation due to heat & use, and metals from wear-in."

These results leave little doubt in my mind that an early fluid change is appropriate.

 

I received my second WS ATF analysis back from R&G labs (was PdMA) yesterday. Total mileage on the transaxle was 19,824, total mileage on the ATF was 10,262 miles (I changed the initial fill at 9562 miles). The new analysis is #311360, the previous one was #283540.

The most interesting part is that the Si went from 147ppm down to 46 ppm. This would seem to confirm that the Si is mostly the result of sealant and other manufacturing sources in the initial fill.

 

Given the used fluid tests taken at various mileages and posted above, it sounds like a good idea to do the first transaxle fluid change at 10K miles; followed by subsequent changes every 30K miles (i.e., at 40K miles, 70K miles, 100K miles etc.)

 

I agree, although I will still probably sample at 25k and 30k just to see how the Fe and Al levels are. I plan to change again at 40k unless the analysis suggests otherwise.

 

Everyone has their favorite data points and mine are viscosity:

24.6/5.5 - 40C/100C virgin
23.6/5.2 - 40C/100C first change
23.9/5.3 - 40C/100C second change (GREAT!)

The target is to change the oil just as the viscosity loses about 15%:

20.9/4.7 - 40C/100C 15% down viscosity, time to change

By a straight-line, it looks like you could go 6x between changes, 60k. However, 5x would be a good target for the next change with plenty of pad, ~50k miles of oil service life. But even 60k miles of service life is consistent with the other metrics we've seen for Type WS in the NHW20 transaxle.

Bob Wilson

 

I'm right at 35K miles after 1 year on my 2007. I just ordered a case of Red Line synthetic ATF-WS and plan on making the change in a couple of weeks. Where should I send a sample to get analyzed (I'll pay) and should I just report the results here? Has there been any reported negative side effects from switching to synthetic ATF? I use mostly all synthetic oils in everything I own including the gears and transmissions.

Thanks
Steve

 

Let's face it. Everything breaks down over time... it's called entropy. Now, just how fast if breaks down is predicated on many, many factors - some of which are how hard you drive, how hot the fluid gets, how hot the engine gets, local environmental conditions and temperatures, etc. To say the fluid will last 100k miles is a safe venture - after all, Toyota wouldn't say that if they knew the transmission was going to fail before then. But, common sense says to change the fluid at least once before then. Here in AZ, the summer temps get quite hot and everyone out here will change their motor oil every 3k miles instead of the manufacturers recommended 5k miles.

 

Most people seem to use Blackstone Laboratories for their used oil analysis, I'd recommend them to keep the reports consistent.

I've used them for a while now for engine oil analysis and they seem to do a good job.

 

What do they charge for a 40C/100C oil viscosity test? The reason I ask is someone reported they were pretty high.

The reason for a 40C and 100C oil viscosity test is to see how it is holding up at low and high temperatures. A worn out oil will have a smaller ratio at the viscosity extenders fail. This is something a transaxle has to worry about because it spends more time in the low temperature ranges than does engine oil.

In contrast, engine oil tends to deal with high temperatures all the time. The time it is at a low temperature is very brief. IMHO Blackstone is quite adequate for engine oil but I understand rather expensive when trying to test both low, 40C, and high, 100C, viscosity.

Bob Wilson

 

I'm going to skip the sample that I was going to pull out at 25k; I'm unemployed now and may need the money for something more urgent. Hopefully I will have found work again by the time I reach 30k.