Changing Transaxle oil

I changed the transaxle and MGR ATF WS fluids today on my HiHy at 30K miles and attached a few photos, since I know that some Prius owners also own a HiHy. The photos include:

• US quart bottle of Toyota ATF WS, the pump that I used (intended for gallon plastic containers, but works well with the ATF WS quart bottle), and a funnel that I bought but later decided would not be helpful for this particular job
• view of MGR, showing the fill plug (partially hidden in the shadow to the left) and the drain plug (to the right)
• view of transaxle fluid drain plug (to the left) and inverter/transaxle coolant drain plug (to the right)
• view of transaxle fluid fill plug (to the left) and transaxle fluid drain plug (to the right)

The MGR drain plug has the little circular magnet on the tip, same as 2G Prius. That plug had a small mound of ferrous powder on the tip so I cleaned that off before reinstalling.

The transaxle drain plug does not have a magnet on the tip. It is the same as the fill plug. Both plugs have a thicker "head" as compared to the drain/fill plugs found on MGR or the Prius transaxle.

The old fluid was darker than new but seemed OK, no unusual smell or metal debris noted in the drained oil. The transaxle fluid was probably 1/2 quart overfilled, judging by the stream of fluid that came out of the fill hole when I removed the plug. When cold, the transaxle maintains a partial vacuum, just like the Prius transaxle.

Tightening torque for the drain/fill plugs is same as 2G; 29 ft.-lbs. A 10 mm hex key socket is needed to remove/install all four plugs.

The fluid capacity spec for MGR is 1.9 qt and this seems accurate. The fluid capacity spec for the transaxle is 4.2 or 4.4 qt depending upon whether the transaxle has an oil cooler or not; this seems overstated since I used less than 6 qt of fluid total. The SUV was elevated on four jackstands and as level as I could make it.

 

Patrick

I'm just curious if you needed to raise the HiHy for that job? I test drove a HiHy before settling on my FJ, and to my eye the HiHy has almost comparable ground clearance

At least with my FJ, the only time I jack it up is when I put the winter tires on, or the "all season" tires. Oil changes, transfer case, and rear axle are easy with all 4 wheels on the ground.

The front axle is tight, but that is due to the skidplate and the recessed head bolts. Having it in the air wouldn't help

jay

 

Hi Jay,

It is probably feasible to reach the plugs on MGR without raising the HiHy. However since the transaxle plugs (esp. the fill plug) are at the rear of that assembly, it is necessary to get under the engine so that one can reach those plugs. I think this would be very difficult if the vehicle was not raised up.

A further issue is having enough room under the vehicle so that one can hold the quart bottle of ATF and pump away, without spilling the fluid everywhere. I ended up holding the bottom of the ATF bottle with my left hand and the pump tube leading to the transaxle with my right hand.

The end of the tube has a plastic fitting that is supposed to grab the fill hole, but some oil was dripping out of the hole. I had to hold the tube so that it entered the hole horizontally, instead of at an angle. Then, I compressed the pump handle against a flat surface of the transaxle by pushing the bottom of the ATF bottle upwards.

 

Gotcha, thanks

 

A couple comments. I saw SuperTech Dexron VI at wallymat, and read on bottle it meets both Toy WS and T-IV specs. Not that I would use it to save $10, but is WS really only the new Dex VI?

There was a link to Art's automotive on the forum, and Art ( I presume it's Art) said WS has an affinity for moisture and they take precautions to lessen exposure. I didn't know oils did that, some solvents do of course. If so is that why there is a small vacuum in the housing? How in the heck do they keep a vacuum in there anyway? Do we need to apply a vacuum as we seal the plug?

I have 7K miles in 15 months so have time, like 48 more months, to find out all about WS fluid changing.

 

A couple comments. I saw SuperTech Dexron VI at wallymat, and read on bottle it meets both Toy WS and T-IV specs. Not that I would use it to save $10, but is WS really only the new Dex VI?

There was a link to Art's automotive on the forum, and Art ( I presume it's Art) said WS has an affinity for moisture and they take precautions to lessen exposure. I didn't know oils did that, some solvents do of course. If so is that why there is a small vacuum in the housing? How in the heck do they keep a vacuum in there anyway? Do we need to apply a vacuum as we seal the plug?

I have 7K miles in 15 months so have time, like 48 more months, to find out all about WS fluid changing.

 

Over here the site is respoding so slow I put in two the same posts waiting.

 

Hi Van,

I had not heard that Toyota ATF is compatible with any Dexron fluids. Since the hybrid transaxle has high voltage within and is an extremely expensive component, I personally would refuse the use of any ATF besides the correct Toyota fluid.

Brake fluid is an example of an automotive hydrophilic fluid. If you get brake fluid on your bare skin you will feel a drying sensation.

I an not aware that ATF WS shares this property. The oil feels no different than any other transmission fluid, except for lower viscosity.

The vacuum is formed as the transaxle heats, and a vent allows the excess air pressure within to escape. Then when the transaxle cools, the inside air is at a lower pressure compared to atmospheric pressure. So you don't need to worry about that, except to be aware that a vacuum exists in a cold transaxle and to not be surprised when you open the fill plug and hear a hissing sound as the pressure equalizes.

BTW one should always loosen the fill plug first when doing any transmission or axle fluid service, to make sure that the plug is not stuck. You would not be happy if you drained the fluid and then found that you could not replenish it.

 

Hi Patrick

Just to nitpick; the term for something that absorbs (or adsorbs) water is hydroscopic edit: hygroscopic is the correct term. A hydrophilic material will bond with water but not necessarily absorb it.

One of the only usable concepts I learned in grad school.

 

I tested Amsoil ATF with both a baseline and frequent follow-up testing. But when I saw a consistent pattern of high copper content, I stopped the experiment and warn people off of it.

I have no problem with folks testing other oils _IF_ they setup an oil testing plan to make sure the oil doesn't do something bad. This means a $20 baseline test of the oil and then $20 tests at:

1,000 - miles and flush change

1,000 - miles
2,000 - miles
5,000 - miles
10,000 - miles
20,000 - miles
50,000 - miles

It is also important to do a flush change to dilute the oil that can not be drained, the residual oil. This ensures you have a valid test.

Bob Wilson

 

In a different thread, someone mentioned that they are now using Redline D6 syn ATF. I don't know if he is planning to do oil analysis or not. It is somewhat intriguing because the manufacturer (Redline) claims that it meets the WS spec.

http://www.redlineoil.com/products_gearlubricants.asp?categoryID=8

 

I think testing synthetic transaxle oils is a good thing. They have a uniform molecular weight (if they are truly are synthetic) so they should be less subject to wear. That is why I tested Amsoil ATF but testing is not just dumping it in the car and waiting for something bad to happen.

Right now I am making a study of Type WS in the NHW11 transaxle that normally uses Type T-IV. So far, the results have been unremarkable ... no "Holy SH*T!" moments like when the Amsoil oil analysis came back. But my Type WS tests will take about another 18+ months to complete.

If I decide to try other transaxle oils, the first step will be to have each virgin sample tested. Then I would go with the one with the least amount of additives since this should minimize the risk to the the motor parts. I suspect in 18-24 months there will be many more options.

Bob Wilson

 

Thank you thats me. Redline does make the best GL4 product in the world. My 07 runs excellent with the D6 installed. Its spooky how quiet the car is now. I will pull some at 2K down the road for analysis but I have put there product in at least 10 cars in the last 10 years and I'm sold. There oil has fixed one cranky trans after another.They also make the best diff oil too. Oh and there Water Wetter is excellent too. It changes the surface tension of water. Wouldn't think of running a car in Florida without it. Check out these linkies:

http://www.redlineoil.com/pdf/3.pdf
http://www.redlineoil.com/whitePaper/10.pdf
http://www.redlineoil.com/whitePaper/17.pdf

My friend Rambo:

 

Are you planning to have any oil analysis done on the Redline? Edit: Oops missed that on the first read through. I will be interested to see how it fared in UOA.

Some of us are apprehensive about using another ATF because the electrical characteristics of the WS may be important as well. Bob Wilson was using AMSOil ATF and had bad results as shown by UOA.

I have used Redline in a manual gearbox and differential, so I also like their products. But the Prius transaxle is a unique combination of gearbox and electrical motors, so you are in new territory.

 

Toyota's WS fluid has no electrical characteristics. None. Bob seems to have freaked out alot of people concerning the trace elements he found in his Amsoil UOA. But I would expect to find exactly what Bob found.
But back to the WS. The WS fluid is a high quality low viscosity transmission fluid. Thats it. This fluid was not designed specifically for the Prius. It was in Toyota's arsenal when the Prius was made. Many of Toyota's cars & trucks use it. It has no electrical properties. It is not motor armature wire friendly.The Prius CVT transmission is a very precision machine and would probably be quite happy with 3 in 1 oil in it. The WS fluid sees none of the the torture of a torque converter as in conventional transmissions and in fact is solely a gear lubricant. Which is why the dealer sees no issue on a 100K refill.The Prius trans is unique in that it happens to have motor field windings running through it. These wires/windings have an extremely tough non conductive coating on them to assure that high voltage on these wires is never exposed to the trans fluid which if even a tiny area of these windings was exposed would result in catastrophic failure of the motor and or inverter.Actually.... forget trans fluid. Have you ever seen a wound armature? The wires are wound extremely tight to each other. No matter how hot they get there non conductive coating rarely fails and allows adjacent wires to short out together. It happens but its rare so needless to say hot trans oil has no effect on these wires whatsoever.
Bob's Amsoil UOA revealed high copper content which he assumed meant that he was seeing leeching from the motor wires. Which has to mean the raw copper current carrying portion of the windings was exposed to fluid and failing.We talked at length about this and I contend thats not possible. Not without failure of the trans. Even exposing a tiny portion of the field wire to trans fluid would result in at least crowbarring the inverter. And I bet he's motoring down the road quite happily as we speak. I believe what he was seeing was exactly what high quality synthetic lubricant does. It captures residual contaminants...keeps those contaminants in liquid suspension as compared to inferior lubricant that under heat just bakes it to the metal. In this case the residuals was simply bearing wear. I give you exhibit A any motor that has spent its life running Mobil 1. Tear it down and wipe it off & you can eat off it. Try doing that with any oil thats not a synthetic. I bet if he hadn't freaked out but flushed out that first round of Amsoil and went another round he would find an excellent UOA. I highly doubt that Amsoil product contains any chemical that would have any effect on the motor windings. These wire coatings are really tough. Its just my opinion but I will guarantee you that any compromise of the MG1/2 motor windings will result in damage to the motor or inverter no matter how slight the compromise.
I do not expect to see any trace elements in my 2K UOA of my Redline sample as the car only had 6K on it when I changed over.
You mentioned you had good luck with manual trans Redline oil. I did too. There MT-90 is amazing isn't it? I learned about Redline when I had some high performance Nissans and I frequented Freshalloy.com and learned what the tuners were using. Its a unique product in that it actually works!!

 

I am looking forward to seeing the Red Line results. For virgin oil samples, the viscosity falls between Type T-IV and Type WS:

cSt@40C / cSt@100C / index
7.4 / 35.3 / 183 - Type T-IV (PdMA)
6.4 / 30.7 / 166 - Red Line D6 ATF (pdf specifications)
5.5 / 24.6 / 171 - Type WS (PdMA)

Higher viscosity lubricants tend to reduce vibration and noise resulting in a "smoother" and quieter operation. But sometimes this can come with higher viscosity losses. But viscosity losses are difficult to measure.

One question still open is how much oil remains in the NHW20 transaxle after an oil change. I was able to use the test results from the old oil and new oil to get a good estimate for how much is carried forward in the NHW11 after dropping the pan, ~15%, based upon the viscosity dilution.

As for the aborted Amsoil test, the copper had a disproportionate increase relative to the other wear materials, iron and aluminum. If all wear materials had been in the same ratios, the 'suspension' hypothesis would have more merit. Sad to say, tin, the other element found in bushings was at such low levels, the limits of detection, I could not say where the copper was coming from so I don't rule out bushings.

The new Amsoil ATF has high viscosity, similar to new Type T-IV, and the oil tests showed viscosity losses that I suspect comes from shear-down. Viscosity reducing, shearing-stress would also be experienced by the bushings and accelerate wear. Bushing wear is not something an NHW11 transaxle should have. The newer NHW20 transaxle replaces the few NHW11 bushings with bearings, a better solution.

I remain concerned about conductive contaminates. Unlike a mechanical transaxle, the NHW11 regularly has voltages of ~300 V. and the NHW20 has voltages of ~500 V. Conductive contaminates, depending upon hardness, can abrade insulation when 'sling' cooling the windings and might provide the 'last leg' in a spark gap. IMHO, it makes sense to minimize conductive contaminates in operating oil. At least in my transaxle it does.

Bob Wilson

 

Let's remember that the NHW11 transaxle has several more
bronze sleeve bearings, which were replaced with ball bearings
in the NHW20. There's your copper.
.
_H*

 

All materials have electrical characteristics.

Like I stated above, I will be interested to see your results from UOA.

 

How old is Rambo? He is very cute.

 

Walmart brand Supertech D6 claims to meet WS spec, so my question is: where does Toyota get the oil in their black bottle they sell to us? It is as good as the "genuine" engine oil they sell? Most Supertech oils seem to be made by Warren Peformance Products, and I do think they make good oils. I am wondering if Toy just repackages the Warren D6. Is the tin can WS sold some places made in Japan? Warren oils seem to have a "WPP" on the plastic bottle bottom.

With old lathes often the bearings were precision bushings. With a good oil film they last and last, some for 100 years and still running smooth. Ball bearings are lower friction, but as everyone knows, dirt kills them fast.