Big transmission dilemma

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My goodness, you're not going to believe this. Toyota recommends T-IV *AND* ATF WS for the exact same automatic transmission, depending upon Camry model year.

The 4-cylinder 2005 and 2006 Camrys have the Aisin U250E transmission, whereas the V6 Camrys have the U151E.

One year later for 2007, the newly styled "next generation" Camry with 4 cylinders (same 2AZ-FE engine as the 2006) also uses the U250E transmission, but instead of T-IV, Toyota specifies ATF WS for the '07 model year!

So here we have the two exact same transmissions, the U250E, but Toyota specs T-IV in the 2006 model year, and specs WS in the 2007 model year. The two fuids are not suppose to be interchangeable.

Here's a quote from GearsMagazine:

"One very important thing to remember is that the U250E requires
ATF WS:

ATF WS is used to reduce the resistance of the ATF and improve the fuel economy by reducing its viscosity at normal operating temperatures. At higher fluid temperatures, the viscosity is the same as that of ATF Type T-IV, which ensures the durability of this unit.

"ATF WS and other types of ATF (ATF Type T-IV, D-II) aren’t interchangeable. So with ATF WS you get improved fuel economy and durability and that’s not only smart... it’s street smart!"[End quote]

Here's the link to the article in GearsMagazine.com :
http://74.125.45.132/search?q=cache:GWcY...n&ct=clnk&gl=us

And here's a link to TransTec which verifies that the U250E is used in both the '06 and '07 Camrys.

http://transtec.com/selector_guide/Toyota.htm

Finally, if you find it difficult to believe that the U250E transmission in the '06 Camry and the '07 Camry is the EXACT same transmission, check out this really convincing PDF document that shows the gear ratios, fluid capcity, and weight of the transmissions in both the '06 and '07 Camry:

http://www.google.com/url?sa=t&source=we...K3HJ53uSZ77sa_Q

My '06 manual specifies using T-IV, but I also happen to have a manual for the next gen. Camry (in this case the '08), and it specifies WS.

I've already replaced half of my car's T-IV with Mobil 1 Synthetic ATF, but maybe a WS fluid would work just as well? Whaddya think? Should I buy a WS or T-IV for my next fluid change later this week? If a WS, I'll do an ATF oil cooler line complete flush, instead of just a drain-and-fill.

For the U250E transmission, how can Toyota recommend two very different ATF fluids that are not suppose to be interchangeable?
 
Maybe they changed the composition of the internal clutches and redesigned the flow circuits for the fluid.
 
I had a similar rant but for the DexIII and T-IV. Looks like Toyota is at it again. Same transmission but they recommend 2 non-interchangeable ATFs.

If they made significant changes to the tranny they would have/should have gave it a new model designation.
 
Originally Posted By: Boomer
Maybe they changed the composition of the internal clutches and redesigned the flow circuits for the fluid.

+1

Can't tell it's exactly the same thing just based on gear ratios, fluid capacity, and weight. There's a lot more to a transmission than that, especially an automatic.
 
You might be right, but the weight for both transmissions in the '06 and '07 Camry is shown to be the same 205 pounds. Wouldn't there be at least a one or two pound difference--maybe much more--if the composition of the internal clutches were changed, and the flow circuits were redesigned?
 
Some car engines went from a 5W30 to a 5W20 for the exact same engine (year to year) basically in an effort to get better CAFE figures. Maybe in these transmissions they figured that they could do something similar?
 
Originally Posted By: Donald
Some car engines went from a 5W30 to a 5W20 for the exact same engine (year to year) basically in an effort to get better CAFE figures. Maybe in these transmissions they figured that they could do something similar?


Bingo. We all know that most engines can safely be switched from 5W30 to 5w20 as 5W30 shears down to 5W20 rapidly anyhow. Similarly, traditional dino ATF shears down from 7.X cst (100C) to 5-6 cst without too many negative consequences. The idea is start with lower viscosity fluid that is shear stable and enable better fuel efficiency and longer drain intervals.

This is exactly what Toyota did. There are some problems with that though. Even WS is not shear stable and can go from 6 to 4 cst. There are a lot of complains on RAV4 forum with front diff whining in V6 models during summer (too thin ATF IMO). It goes away with thicker ATF.

This is why I don't trust lower viscosity lybricants entirely. There is always a compromise between fuel efficiency and wear protection when one manipulates viscosity.
 
Originally Posted By: Donald
Some car engines went from a 5W30 to a 5W20 for the exact same engine (year to year) basically in an effort to get better CAFE figures. Maybe in these transmissions they figured that they could do something similar?


..but 5w-20 and 5w-30 are fully compatible with each other.


I can see this being a nightmare if there are some true conflicts between these two fluids. Suppose Joe who knows who tops up with WS with T-IV ..or whatever?

The Amsoil reference guide shows the same change in fluid spec's for both transmissions offered in the Camry from 2006 to 2007.
 
Originally Posted By: Built_Well
I've already replaced half of my car's T-IV with Mobil 1 Synthetic ATF, but maybe a WS fluid would work just as well? Whaddya think? Should I buy a WS or T-IV for my next fluid change later this week? If a WS, I'll do an ATF oil cooler line complete flush, instead of just a drain-and-fill.


Stick with Mobil 1. WS is not synthetic and starts to shear by 30K miles.
 
Originally Posted By: Ursae_Majoris
Originally Posted By: Built_Well
I've already replaced half of my car's T-IV with Mobil 1 Synthetic ATF, but maybe a WS fluid would work just as well? Whaddya think? Should I buy a WS or T-IV for my next fluid change later this week? If a WS, I'll do an ATF oil cooler line complete flush, instead of just a drain-and-fill.


Stick with Mobil 1. WS is not synthetic and starts to shear by 30K miles.



I have been told WS is a synthetic
 
Originally Posted By: PT1

I have been told WS is a synthetic


When T-IV came out I was also told it was synthetic. Well, it was not. Same with WS. Maybe it is group III fortified?

Interesting how Toyota strongly cautions not to mix these fluids. Yet, the only difference that we know for sure seems to be viscosity.
 
Originally Posted By: Built_Well
You might be right, but the weight for both transmissions in the '06 and '07 Camry is shown to be the same 205 pounds. Wouldn't there be at least a one or two pound difference--maybe much more--if the composition of the internal clutches were changed, and the flow circuits were redesigned?
Sometimes the only difference is programming. Same transmission, different codes to control shifting.

I'd buy Amsoil ATF, and I wouldn't be afraid of the low viscosity version.
 
Thanks, but I already made up my mind to stick with a suitable T-IV replacement like Mobil 1 Synthetic ATF (or Red Line or Amsoil, but not the WS-like low-viscosity version :)
 
hate2work, what PN's are you talking about? Please post 'em and research them at your local dealer's parts counter.
 
The part numbers are in the link I posted. Below is an excerpt from Built-wells post from that link. He had started a similar thread on another forum, and somebody ( Ray ) came up with the idea to check and see if the clutch parts were the same.

==============================================================

As usual, it takes a smart man like Ray to shed light on the
subject. The part numbers are different for the clutch discs found
inside the '06 and '07 U250E transmissions. According to
ToyotaPartsAndService.com, the '06 clutch disc has a part number of
31250-28181, whereas the '07 clutch disc has a part number of
31250-33040.
 
Originally Posted By: unDummy
Manual transmission clutches have how much relevance in this thread?


Ooh, that's a good point. I just checked my book "Auto Upkeep." Clutches are used in manual transmissions. Torque converters are used in automatic transmissions.

So I guess I gotta ask why Boomer mentioned the following:

"Maybe they changed the composition of the internal clutches and redesigned the flow circuits for the fluid."

That statement put me on a wild goose chase for clutch part numbers when there actually are no clutches in the U250E automatic transmission.
 
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