ZVW30 Transmission Oil Analysis

[bwilson4web]

Hi,

I am a great fan of analyzing transmission oil because unlike engine oil, it tends to stay in service at least 10 times longer. Furthermore, earlier studies of transmission (aka., transaxle) oils revealed the NHW11 service interval needed to be shorter, 30k miles instead of 60k. The NHW20 using Type WS looks to be working fine at 60k miles.

When I took my wife's ZVW30 in for the first change, I had the transmission oil changed and got a sample, about a cup. It was opaque but still smelled like oil. For sure, I wanted to remove the initial SI leached from the sealant as well as the early 'lapping' as the gears wear in. Also, I am very interested in seeing any evidence of oil oxidation (more about this later.)

Here is the initial sample report and there will be updates in the future. Oh and one last thing.

I am no longer in the business of collecting oil samples from others and sending them out to be tested. In the past that was the fastest way to collect a population of oil samples at different mileages to understand what was going on. But the ZVW30 is new, less than four months in North America.

If you want to participate in this study, feel free but please arrange for your own samples to be send to a quality lab for analysis. I have history with R&G and they provide 40C and 100C viscosity testing, which I think is an important metric equal to the wear and additive content.

Go here if you want to see a reference sample of Type WS and why transmission oil testing is important.

Enjoy,
Bob Wilson

[bwilson4web]

Ok, this is the oil analysis that I'm interested in:


Ok, the reason I'm interested is to find out how the viscosity decreases over time. I spoke with James, the lab tech, and we're going to do some special tests to look for micro-dieseling. Micro-dieseling is a type of oil oxidation. We're also going to check the particle load.

ANALYSIS

The goal is to estimate the miles to a 15% loss of viscosity:

C	cSt 0mi	cSt 5kmi	%	miles	~15% mi
40	24.6	23.3	-5.3%	5,000	14,192
100	5.5	5.3	-3.6%	5,000	20,625

.
This suggests the next change needs to be after 15-20k miles of service. This initial rate of viscosity loss is similar to rates seen with the NHW11s.

Other experiments have shown the silicon is leached from the case sealant. The highest concentrations in the past, 227-258 ppm, suggests we've taken out half of the silicon and leached sealant elements.

The iron, aluminum, copper, nickel, and manganese appear to be wear materials but some of them could be leached from the sealant. We'll need another sample closer to 15-20k miles to gain insights. Looking at iron, this rate .0042 ppm/mi is consistent with the .0037 ppm/mi seen with Type WS in an NHW20 transmission. We're probably seeing local spike due to early wear. The next test will give a better idea of the long term wear.

I suspect the boron is boron nitride, an anti-friction additive, that is used up over time. Interesting, I see no evidence of anti-friction, molybdenum suggesting its other characteristics may cause material problems with these transmissions.

It took about four months to reach 5,000 miles. At this rate, it will take a little over a year before taking our second change and analysis.

Bob Wilson

[bwilson4web]

I've gotten the microscopic examination report:

There were a few ferrous cutting wear particles, metallic spherical wear particles, and red oxide particles present on the slide. Also, a few ferrous rolling wear platelet particles, ferrous/nonferrous white metal rubbing wear particles, and abrasive/dust/dirt particles were found on the slide. The presence of cutting wear particles suggests possible misalignment and/or abrasive contamination. The presence of rolling wear platelet particles suggests possible surface fatigue and/or rolling contact due to metal-to-metal sliding and/or abrasive contamination. The presence of red oxide particles suggests possible past or present water contamination. The presence of metallic spherical wear particles suggests possible rolling bearing fatigue and/or welding or grinding processes(contamination). The morphology of the abrasive/dust/dirt particles suggests possible contamination of the sample and/or reservoir from an external source.

(see attached)

We also had a particle count:

4/ml - 99999
6/ml - 9959
14/ml - 18
20/ml - 4
30/ml - 2
40/ml - 0

Mostly we're seeing very small, very fine particles and not much in the larger sizes. These are not in the sizes that an ordinary filter would handle, ~14 u. The smaller particles would take a micro-filtration system and commercial ones are pretty expensive.

The acid number is up a little, 1.49 vs. 1.41, we'll watch it over time. This is our primary indicator of micro-dieseling.

Silicon leaching is evident but lets compare the sealant test, 8 months soaking Type WS in a jelly jar, values and a virgin Type WS sample with those from this change:

element	virgin	ZVW30 5k	sealant
Silicon	3	103	1280
Boron	59	47	24
Phosphorus	245	247	258
Calcium	109	120	124
Zinc	0	10	69

.
My thoughts:

• silicon - sealant is the likely source being leached
• boron - an additive to reduce friction, the loss when exposed to sealant is curious.
• phosphorus - an additive, nothing remarkable, a formulation change?
• calcium - normally an additive, a formulation change?
• zinc - sealant is the likely source, one patent describes using zinc oxide to improve surface characteristics

The red oxide observed may be from the sealant. Dow reports using "iron oxide" in some of their products and the sealant is red in color. However, there was no iron found in the sealant dish test (8 months soaking in a jelly jar.) Speculation on my part, sealant under stress may shed small particles.

There are some reports from Amsoil sites claiming leaching of silicon sealants leads to foaming in oil. But I've not found anything specific.

BOTTOM LINE - IS A 5K TRANSAXLE OIL CHANGE WORTH IT?

This is what I'm after:

• reduced rolling resistance - oil debris increases friction and generates local heat, the enemy of oil
• viscosity tracking - oil wears and loses its ability to reduce drag and protect surfaces ... I want to understand the rate

My early change removed some wear material and sealant leached compounds. Also, there appears to be ~5% viscosity loss after 5k miles. So I feel comfortable going 15k before my next change but this satisfies my curiosity.

I'm not doing transaxle oil changes for extending the transaxle life. The ZVW30 transaxles have been out for less than six months and we have no failure history. The earlier NHW20 transaxles have been very robust with very few documented failures. The NHW11 had one go over 350k miles and the hand full of NHW11 failures have been electrical, not mechanical. But rolling drag is something I do worry about.

My earliest hill roll-down tests showed a measurable reduction after an early transaxle oil change. Given it is a 'free' drag reduction, keeping the transaxle oil clean seems like a small price to pay. Not to worry, the used oil is recycled.

Bob Wilson