Transmission fluid change?

one thing I will point out on it being a sealed unit is condensation. Unless you get the unit up to temp it might contaminate the fluid. Rick being in PHX, temp will not be a problem.

 

Frank:

DING! You get the Gold Star for pupil of the week.

Seriously, do you think that is why the Canadian Prius supplement requires the CVT fluid change? I do know that with conventional automatic transmissions, you will get condensation if operated in temps of -40.

 

it's probably one of the contributing factors on the change requirement as Toyota has no idea where the car will end up being delivered so just do a blanket recommendation. Then I think Kansas and the coast of BC and why don't they have the same recommendation as the CDN models? So it' probably blanket for Canada and they take their chances with all US models.

 

Good point. Also Minnesota and the Dakota's. If in doubt, service it. Cheap insurance.

 

I just crawled under the car yesterday and changing the fluid looks like a potential do-it-yourself kind of thing, no harder than changing oil (which I do).

Remove drainplug (looks like it needs a 10mm hex, can anyone confirm?).
Remove filler plug (looks like a 19mm).
Let drain.
Replace drain plug, and refill with ATF WS (long necked funnel will be handy here).
Replace filler plug.
Doesn't even look like any washers are involved.
And the drain/fill plugs are brass which stand out colorwise against the aluminum making it harder to remove the wrong ones.

Is it really that easy? Or is there some additional gotchas that I'm missing?

Thanks,
Shawn
PS Are there torque specifications for the drain/filler plugs?

 

Shawn:

It doesn't appear to be very hard to do at all, does it? Though for as often as it has to be done, I think I'll just have the dealer worry about it.

Do you have one of those pumps that fit onto a quart bottle? I have one that works very well for pumping fluids into places that are very hard to reach.

It won't pump 80W-90 gear oil at -20, but for thin fluids it seems to work well.

The torque specs should be in the service manual. I sure as h*** wouldn't try to overtorque the bolts, you'll either strip the threads or possibly crack the case.

Yes, there was a warning on my 2000 GMC Sierra with the Autotrac transfer case about that. The transfer case was made out of magnesium. Cheap b*******.

 

Yeah, I'm still debating the dealer thing. I'd probably would be doing that, even for oil changes, if I hadn't seen their special for changing the cabin air filter: $64.95. Now, I know it's a $20 item and they should make a profit, but come on, it takes all of 90 seconds to change.

No, but it sounds as though it might be just the thing. I'll look into it. Thanks much for the tip.

I do worry about stripping the threads (or worse), and I don't have the service manual (still debating on downloading vs published), yet.

Again, thanks for the tips,
Shawn

 

Just thought I'd put a few details out there to share a little knowledge. I'm an automotive engineer, GO VA TECH!, and have actually designed several CVT's. There are many different styles, and the one in our Prius' is a simple chain/belt type. A specially designed linked looking belt rides on toroidally shaped (think cones), a pair on each end. As these move apart, and close together, the belt goes higher or lower in between the cones. The special $50 fluid is a special fluid that had to be developed, many years ago, when CVT's were in their early stage. The reason is, that the fluid is actually what drives the car. I know, I sound nuts. Their is supposed to be no metal to metal contact in a CVT. The belt "rides" on a very very thin layer of oil that transfers the power. It's one of many reasons that CVT's are power limited--there are many more, but the fluid is one of them.

The only parts really that could see metal shavings are from the planetary gear driveset at the output. I agree, that nothing is really "lifetime", but I'm certainly feeling safe in not changing my fluid until 100k miles. Don't sue me or anything, but that's what I'm doing. At that time, I would use a pump to make sure that I changed all of the fluid. I would change the fluid partly for particles, but mostly for oil breakdown from temperatures, any condensation or water vapor that may have formed, or other degredation of the fluid molecule chains.

My Audi also has a CVT, very similiar type to the Prius, and I won't be messing with that fluid until about 80k miles, which is what's recommended by Audi. However, remember that car is pushing 220 hP, which is little higher than the Prius, don't you think?

 

<div class='quotetop'>QUOTE(BrianJ @ Jan 27 2007, 03:03 AM) [snapback]381609[/snapback]</div>

That is incorrect. The Prius does not have this type of a CVT. A planetary gear power splitting device is used in the Prius in lieu of a transmission.

 

<div class='quotetop'>QUOTE(BrianJ @ Jan 27 2007, 06:03 AM) [snapback]381609[/snapback]</div>

Perhaps, but apparently not a very well informed one.

 

<div class='quotetop'>QUOTE(Tempus @ Jan 28 2007, 06:41 AM) [snapback]381911[/snapback]</div>

That's ok... he is probably the one who designed the transmission in your OTHER car!

 

Hummm, a little bit of FUD in the thread. Let's throw in some facts and data:

• NHW11 - uses Type T-IV and has a pan that can be dropped and cleaned.
• NHW20 - uses Type WS, much improved oil but has no pan to drop.

For those with an NHW11, the following web page has some photos to help you DIY change the transaxle oil:

http://hiwaay.net/~bzwilson/prius/pri_T_cold.html

I have collected some NHW11 transaxle oil samples and one NHW20 oil sample for test and got these results:

http://hiwaay.net/~bzwilson/prius/pri_toil.html

My current thinking is:

1) NHW11 Prius in dusty areas (aka., Texas, Arizona) need to have transaxle oil changed early with dropping the pan. There appears to be a positive correlation with dirt/grit and dusty areas of the country.

2) NHW20 Type WS oil appears to be a reasonable upgrade for NHW11 Prius owners who are willing to run the risks. Its starting viscosity appears to be the same as the worn out, Type T-IV oil viscosities. Analysis suggests a potential savings of 6% over the Type T-IV.

3) Viscosity testing suggests the Type T-IV is only good for less than 30,000 miles. A straight-line approximation suggests as little as 15,000 miles BUT your mileage may vary.

I am testing a transaxle breather tube modification but do not have results to post, yet:

http://hiwaay.net/~bzwilson/prius/pri_vent.html

One last thing, there are no cones in the Prius transaxle. The Hondas use cone-based, CVT transaxles. Toyota is being sued for a possible patent infringement in Florida by a company that makes "electric wheels" and things they patented the idea first. The world waits and wonders.

Bob Wilson

 

<div class='quotetop'>QUOTE(bwilson4web @ Jan 29 2007, 02:46 PM) [snapback]382494[/snapback]</div>

Bob, I am not sure the breather tube idea is a good one. You are now purposefully introducing a slight vacuum to the transacle - basically, the pressure drop across the air filter. Also, based on the reported hiss from removing the vent cap - the transaxel gaskets are obviously holding (both a positive or a negative pressure.)

Bottom line, I don't think you made things worse - but just not necessarily any better.

By the way, do you have an opinion about changing the transaxle fluid for the '06 model? any sense of the interval you might recommend?

thanks, John.

 

<div class='quotetop'>QUOTE(John in LB @ Jan 30 2007, 03:30 AM) [snapback]382705[/snapback]</div>

I'm of the opinion it is always a significant, negative pressure because of the one-way valve action. Regardless, I'm satisfied with the theory of the vent tube. If the next oil change comes up 'clean', I'll be happy.

<div class='quotetop'>QUOTE(John in LB @ Jan 30 2007, 03:30 AM) [snapback]382705[/snapback]</div>

I only have one sample from a 2004 Prius driven in Conn., a relatively low dust area. It had gone 60k miles and the 14% viscosity loss was 'right on the numbers.'

What we really need are more NHW20 transaxle oil samples but I haven't been actively seeking them. I had a vested interest in testing the NHW11 oil and paid for several tests. I don't have that motivation for the NHW20. It is the 'problem of the commons.'

Bob Wilson

 

<div class='quotetop'>QUOTE(bwilson4web @ Jan 30 2007, 09:37 PM) [snapback]383167[/snapback]</div>

Semi-related topic Bob.

Following in this thread or another of your's (if not in your thread, a link), it was indicated that with the NHW11, you could remove and clean the pan, but not with the NHW20 (which is in my '05 Prius). Presumably there is a drain plug, but do you know if there's a filter that can be removed and cleaned or replaced, assuming the bottom of the pan can't be cleaned? With only 40k miles, it's not an issue now, but may become one in the future. I expect to keep this car running at least through 200,000 miles.

Thanks.

Dave M.

 

<div class='quotetop'>QUOTE(dmckinstry @ Jan 31 2007, 10:55 AM) [snapback]383317[/snapback]</div>

The photos and comments I've seen indicate there is no pan in the NHW20 models. I suspect there is metal screen on the take-up tube like the NHW11.

My thinking is test the oil along the way. If the test just shows a viscosity loss, no problem. If there is evidence of dirt/grit, I would start thinking about how to do some sort of flush . . . NOT something I would look forward to.

Bob Wilson

 

<div class='quotetop'>QUOTE(BrianJ @ Jan 27 2007, 06:03 AM) [snapback]381609[/snapback]</div>

Nope, no snowmobile transmission in our Prius cars. These photos may assist you, the middle is of Oak Ridge National Labs teardown of a current model Prius. Other photos clearly show the PSD

As far as oil, yes I believe you. In something like a conventional differential with hypoid gears, the oil film is also critical to load carrying and durability. Try to run dry a differential and see how far you get before the ring teeth or pinion teeth shear right off.

Another problem is faced in extreme cold, when an oil may "channel" and not slump/flow. A synthetic gives you much better margin against cold failure, but at very extreme low temps an auxilary heater is needed.

Hope we haven't scared you off, you seemed nice enough ...

 

Not mentioned in this thread, or recently, is that Mike Beyer ('IFixEm' here) has designed an external fluid filter for Prius transmission/PSD/HSD/whatever you want to call the thing. A few such have been installed including my NHW11 which now has type WS fluid, and about 10k miles since the filter installation. I have not done fluid analysis on it yet, but for sure it's not leaking. THe big (let's say >20 micron) particles that the pan magnet does not capture will presumably get held in that filter, and my next fluid analysis will be interesting. But not necessarily representative of 'filter-free' Prius.

 

<div class='quotetop'>QUOTE(tochatihu @ Feb 1 2007, 10:57 AM) [snapback]383878[/snapback]</div>

I thought Frank Hudon did?

 

<div class='quotetop'>QUOTE(jayman @ Jan 31 2007, 07:55 PM) [snapback]383609[/snapback]</div>

Could you point me at the source of the Oak Ridge tear down photo source? I try to follow them closely and thought I had all of their current reports. But this photo has something not shown before, the transaxle vent plug.

Thanks,
Bob Wilson