2001 Prius transmission failure

Hi All,

The motor in the Gen 1 Prius runs at 279 volts, versus 501 volts in the Gen 2, so for the same power the current is 1.8 times more in a Gen 1 Prius. But there are fewer windings of larger wire in the motors, too, to match the larger current requirement. I am not sure if the lower current has an advantage or not.

Another thing is the Gen 2 Prius motor is a "Hybrid Field" motor. That is it gets its field from both permanent magnets, and induction of current in the iron core. Which is how the Gen 2 Prius gets its mid-range punch. The Gen 1 Prius gets the majority of its field from larger permanent magnets in the motor core. So, the amount of field does not increase much versus RPM. Which means mid-range currents need to be higher than in the Gen 2 for the same accelleration.

So the two motors are technically very different things.

I am disappointed Toyota is not honoring a 100 K mile warantee on the motor. At least for cost of the replacement part, prorated, and half the install cost.

If the winding is running hot, other solutions as indicated by JK450 indicates might be tried. Replacing the fluid would be one. Can the pickup tube be inspected with the pan off ? The Gen 1 Prius has a transmision pan, its probably was not wise to leave out a trans dip-stick consequently. So, there is no way to know if the car has been running with low levels of transmission fluid. Flushing the inverter cooling loop might also help. As the inverter is mounted to the transmission, and has many small covoluted passages that could become clogged. Also, why the pan is dropped, one might be able to inspect the electrical connections to the MG2 winding? If one was cracked, or loose, the current through it would be a hot spot which would over time heat up that winding allot. This might be fixed with the transmission in the car, too.

 

As time passes by, I'm starting to see that transaxle failures are not very rare anymore. I admit that this isn't very comforting if I plan to keep the vehicle for more than 100k.

 

<div class='quotetop'>QUOTE(clintd555 @ Sep 7 2007, 08:23 PM) [snapback]508830[/snapback]</div>

I'm not worrying too much. These failures are in 2001-2003 models. I can't recall a failure of a 2004+ transaxle. Toyota improved the design in 04 and also specified a new fluid. I would be willing to bet with fluid change once in a while the new designs will be quite reliable.

 

<div class='quotetop'>QUOTE(n8kwx @ Sep 7 2007, 08:49 PM) [snapback]508835[/snapback]</div>

So what about those of us with 2001-2003 models? Are we destined to pre-mature failure with no remedy from Toyota?

As early adopters of a good idea in vehicle design/concept shouldn't we be afforded some insurance against failure. Isn't it our willingness to jump in on this new idea the very thing that made it popular and acceptable?

Feeling a bit left out in the cold...

 

Hi Pkamm,

Well, that is always the risk of the new. But, there is a guy on here who has investigated prolonging the life of his Gen 1. He has recommends pulling the pan and wiping down all the surfaces to remove fine metal debri. Then replacing the fluid with the Type WS. Look for posts by Robert J. Wilson and Hobbit (regarding Jesse's high mileage Prius Gen 1).

Replacing the transmission fluid every 30 K or less miles seems to be the most prudent thing to do to me. Also, getting the battery sealing recall done too. Because, once a cell in the battery is dry, the whole stack will have high resistance. Since all the cells are in series.

In comparison to standard cars, the failures are right at typical transmission life expectations. Since Toyota is covering the battery expenses pretty nicely, you are not going to be out any money that you would not have been anyway, with a standard car. So, there really is no penalty for being an early-adopter, considering the alternative at the time.

 

Besides, you have had free 24 hour roadside assistance for the life of the car. Where anybody with a 2006 or later did not get this.

 

Both generations of motors use both PM and reluctance torque in
their switching algorithms. The real difference is that the Classic
windings [four 3-phase sets around the circumference] are connected
in parallel, while the '04+ is in series [also with a slightly
changed magnet structure and other engineering improvements]. But
that alone doesn't explain why some of the Classics are starting to
fail this way. I think IFixEm saw the first burnt winding, and
there's Florian Steiper over in .DE, and I think a couple of others
have popped up here and there. But then again there's Jesse who's
about to hit 320K and his ol' T-IV must have been in there for a
*long* time before we changed it.
.
I'd like to see a deeper study of the actual failures at some point
and maybe some chemical analysis of how old T-IV fluid interacts
with insulation enamel. The precise spot of where the damage began
may also indicate a design weakness, possibly in where the wires
hook together around the armature or maybe excessive kinking in the
winding path or whatever other common problems could plague motors.
.
_H*

 

Hi Hobbit,

The series/parallel winding could explain a difference. If there is a difference. Which we wont know til the gen 2 fleet gets as old as the Gen 1 fleet is now.

Parallel windings would need to be carefully matched for resistance and impedance and this can be difficult to do. So, the current split could be slightly imbalanced. Resulting in excess current in one of the windings. This might explain the random nature of Gen 1 failures. Some cars going great distances, while others failing at 70 K miles. If one winding happened after a new spool of wire was put on the winding machine, the wire from the new spool being a little different in metalic, and overall diameters, a mismatch in the coils would occur.

A series combination of the windings would not effect the heating variation between the windings nearly as much. As the current in a series circuit is the same througout (same in all windings). So, the design current could much more reliably controlled.

On the reluctance designs - have you seen sections of a Gen 1 and Gen 2 motor cores? I saw some diagrams which had two slanted magnets in the Gen 2, and a single magnet larger than the two Gen 2 magnets together in the Gen 1 - in each pole. But I do not know if these changes were actually implemented into the production motors. The paper's author said Toyota should be implementing the improved reluctance design in the next gen Prius. The advantage of the slanted magnet design was an increase in mid-RPM magnetic field strength and motor torque, even though the amount of permanent magnet material was reduced.

 

<div class='quotetop'>QUOTE(donee @ Sep 7 2007, 07:21 PM) [snapback]508811[/snapback]</div>

I am not sure I understand the subtleties here, but it sounds like there may be some "interpretation" involved in making the distinction between a "transmission" and the "motor." If Toyota has a 60K warranty on the transmission, and a 100K warranty on the motor, then this interpretation would become critical to evaluating whether or not your vehicle was covered when a failure occurred.

All I know is that a failed transmission on any vehicle made after 2000 (even a cheap American brand) at 91K would be suspiciously early. On a Toyota, it would seem to be a defect.

I have higher expectations from Toyota. I want to be a positive spokesperson for hybrid technology in general, and Toyota specifically for being one of the first to make this feasible for the auto-buying public. But if they screw me with my 2001 Prius now, they will receive much more than the $4800 cost of my "transmission" replacement cost in negative PR on the web from me. The one thing I do understand very well is web technology and social networking. I will use my expertise to the full extent.

I will also keep you folks informed of my progress in this matter. Supposedly, I will be getting a phone call from a Toyota rep on Monday to resolve this matter. We'll see.

-Patrick

 

<div class='quotetop'>QUOTE(pkamm @ Sep 8 2007, 12:10 AM) [snapback]508937[/snapback]</div>

Don't feel too cold. There is a solution. You should religiously change the transmission fluid every 30k miles.

Not all 2001-2003 models are dying, but some are. A regular fluid change is cheap insurance.

I'm impressed overall with the reliability of this new technology. Enjoy your early adopter status!

 

Hi Pkamm,

Can you show me some reference that automatic transmissions since 2000 have been very much more reliable? It seems not credible to me that somehow the age-old technology of these transmissions is somehow different in the last 7 years.

 

For now, as end-users, all we can do is change the transmission fluid and hope for the best. Only Toyota (under warranty and negotiated post-warranty replacements) is in a position to analyze the failures. As such, it is disappointing that they have not decided to issue any official recommendations on fluid service life.

If they are learning how to make hybrid transmissions better, that's great. But I shall not be shouted down for reminding Toyota, after every NHW11 transmission failure, that we are 'in this together'. Here's hoping that such failures remain few in number.

Meanwhile we do replace the transmission fluids, because the old stuff comes out somewhat degraded, and because heck it can't hurt.

 

<div class='quotetop'>QUOTE(donee @ Sep 8 2007, 07:57 PM) [snapback]509287[/snapback]</div>

No reference off hand. But think for a moment. Do you know of anyone with a 2001+ vehicle with less than 100K who has needed a transmission replacement?

I'm sure there are numbers out there. But common sense speaks loudly here.

By the way, Donee, in the name of full disclosure, do you have any fiduciary relationship with Toyota or any of its subsidiaries?

 

<div class='quotetop'>QUOTE(pkamm @ Sep 9 2007, 02:16 AM) [snapback]509395[/snapback]</div>

Hi Pkamm,

No fiduciary link to Toyota here. The Prius was the first Toyota I bought. The closest fiduciary link to a car company might be to Chrysler, as my dad used to work for them in the 60's, but not on cars.

Making blanket pronouncments like that is just plain obviously faulty. Its common sense that these transmissions are going to keep failing as they previously have. In looking for hard data on the internet I could not find anything, but I did find a few web sites that said to the effect " the modern automatic transmission is the most complex piece of machinery on cars today", and then went into the hydraulic, electric/electronic, mechanical and fluid dynamical components.

As your car has 15 K miles per year on it, which is 18 K miles more than the typical driver would have in 6 years, we have to ask not if a 2001 has failed transmission, but if a 91 K mile car has failed transmission. You have put the mileage on your car typical of a person who bought a car a year and a half earlier. So, that would be 1999. There is a girl at work who traded in her 2000 Grand Am and bought a new car because the transmission went. She was thinking she was going to keep the car to 120 K, but traded it at 90 K. My 1988 Tempo transmission failed at 85 K miles. My 2000 SL2 had transmission problems the first year I owned it (lock-up torque converter).

I do not see any AAMCO shops closing down around here either. You know there is a whole aftermarket industry of automatic transmission rebuilding shops in the U.S. , right ?

 

<div class='quotetop'>QUOTE(donee @ Sep 8 2007, 02:32 PM) [snapback]509141[/snapback]</div>

Actually, parallel windings are a common practice in motor/generator/transformer designs. The problem you are describing is not significant. The extrusion dies for wires are extremely well controlled. The difference in resistance between two long wire runs usually varies by much less than 5% and this is engineered into the design. If you look at the resistance per 100 ft on wire specifications, the accuracy is usually to two decimal places.

The DOE reports showed the "V" design was incorporated on the production MG2.

 

<div class='quotetop'>QUOTE(donee @ Sep 9 2007, 07:02 AM) [snapback]509476[/snapback]</div>

Hi Donee,

Well, it would be interesting to find some data on transmission failures generally, and Toyota transmission failures specifically. It would be a sad state of affairs if we have become accustomed to spending 20K+ on a vehicle and then expect to have to invest an additional 5K on it before 100K miles because of a transmission failure. Instead, I'm hoping this is a rare occurrence with Toyota vehicles. But from the posts here and at other Prius forums, it may not be so rare for the 2001 Prius.

Is there an easy answer to making the distinction between motor and transmission on the 2001 Prius? (The difference between a 60K and 100K warranty.)

 

I would recommend you search on this site for "bwilson4web" entries. He is researching transaxle fluids/failures/and other aspects in great detail.

 

Interesting idea on the parallel winding imbalances, but I'm tending
to side with FL_P_D here, especially considering that a warmer
winding's resistance would tend to go up and possibly shift things
back unless the mismatch gets really off.
.
Yup, I've seen the magnet structure diagrams, in the oakridge/
argonne papers and Toyota's "new car features" and some related
and unrelated patents. The vee thing is a "buried magnet" technique
to concentrate and increase flux strength where it's needed, from
what I understand, as well as better help guard against demagnetization
or ripping the elements out of the rotor. Compare against Honda's
IMA, a much simpler rotor with surface magnets and a band of
fiberglass wrapped around the whole thing to prevent them from
flying off.
.
Well, hopefully the mystery will be solved someday and not at the
cost of too many more failed Classics...
.
_H*

 

<div class='quotetop'>QUOTE(pkamm @ Sep 9 2007, 12:09 PM) [snapback]509551[/snapback]</div>

Overall Toyota transmission failures won't tell us much about the hybrid transaxles...
<div class='quotetop'>QUOTE(pkamm @ Sep 9 2007, 12:09 PM) [snapback]509551[/snapback]</div>

Such posts are informational as case studies, but as statstics, they are meaningless unless we know how many folks, by comparison, have no transaxle troubles. And there's no reason for them to post and report on that: " just wanted to tell everyone that my Gen I has 90K and NO tranny troubles. Fuel pump relay is good, too."

Returning to the real world, my experience is that both generations of Prius transaxles are at least as reliable as the average transaxle, if not more so. I do recommend fluid changes at 60K, however.

 

<div class='quotetop'>QUOTE(jk450 @ Sep 10 2007, 01:49 AM) [snapback]509923[/snapback]</div>

Your observations about gathering statistics from posts is valid, though a bit obvious. You'll note that I never suggested gathering this data from posts--that was your assumption.

I'm still not clear on some of the terms used in hybrid cars. Is a transaxle considered part of the transmission? Is there any part of the motor that could be considered part of the transmission?