3rd gen Transmission Cooler Upgrade

These charts are fuzzy. I can't really read them. Can you repost or send a link? Thanks.
It would be totally cool if a solenoid could be mounted on that thermostat so you change it on the fly!!

 

No problem! I didn't have my scangauge the the whole first year of towing our travel trailer. Do you mind me asking what kind of readings you get while towing? I get a little paranoid knowing that transmission runs warm and towing here in the desert.
I can't really say that 190s°F is a bad thing though since nobody's blown an AC60 up yet. I just don't wanna be the first. Who knows though? People hated the 12v cummins when it came out but now that its almost 30 years later they are more valuable than gold lol

I think that's a great call changing out the the fluid every 30k for trucks that work harder!!

BTW taking the trailer to the lake tomorrow so will post some results after the weekend. Also thought this was interesting. It was about 65°F this morning on my way home. I was cruising about 70mph in 6th gear and noticed bolth pan and torque converter temps where staying identical at 146°F so the torque converter had to be locked up at almost 50°F under the normal 190°s!?

 

Pm'd

 

My hottest temps were 208....Stock. but what worries me is the fact that those temps are relatively cool outside temps 60-70°. I bought my truck September 2016 so I haven't had any hot days yet.

 

Awesome thanks for the info!!

 

Am I missing something here? So if there is a transmission thermostat wouldn't that mean that it doesn't activate the stock cooler until the designated temp...Thereby meaning the additional cooler you connected after the stock cooler would only be of use if the thermostat was pinned open? I started up my truck this morning and drive about 12 miles....The temps were 168 & 175. My stock tranny cooler was cold to the touch (because the thermostat hadn't opened up yet). Again, wouldn't that mean the extra cooler is only good when the thermostat is pinned open? I would assume that if the thermostat opened on its own the extra cooler would allow the fluid to cool much quicker.

 

So the thermostat should be partially open even when the transmission is ice cold. This because the transmission oil passes through a chamber in the radiator before moving into the air heat exchanger. This actually helps warm the transmission up faster since the engine coolant gets up to operating temperature allot faster than the transmission.
I've been trying to find out when the transmission thermostat is fully open. I'm guessing somewhere around 185-190°F. Once the transmisson fluid hits that temp fluid would be flowing freely regardless of a pin.
With no pin placed and the thermostat operating as toyota had designed it the extra cooler should help to keep the tranmsission operating at its "normal" 190°F and prevent an extreme heat event. I've actually already seen some evidence of this with the scangauge. The torque converter temps still spike higher but the pan temps stay allot more steady around 185-190°F with the bigger cooler. Before the pan temp would rise up to the torque converter temp or close to it and they would both slowly drop together.

As far as why your heat exchanger was cool to touch may be because of fluid viscosity. I'm speculating here but 170 isn't all that warm for most transmissions and some heat exchangers have larger channels in them that allow cooler fluid to bypass most of the heat exchanger and prevent over cooling. Once the fluid gets hot enough it becomes less viscous and more easily flows into the cooling channels. I know the hayden cooler I'm running has this so maybe the toyota oem cooler may have a similar design to help with warm ups and prevent over cooling. Again just speculation.

The pinning of the t stat for me has been just sort of a test to find normal operating temps. Toyota engineers could've designed a T stat to keep the trans much cooler but chose to keep normal operating temps around the 190°s. I believe the higher temps mean less viscous fluid, less friction and higher MPGs

 

Im wanting to check my transmission fluid level. The main thing I have understood is that you check it when the temps are between 104-111 degrees. I'm curious why Toyota designed the thermostat to even have the ability to pin it open.

 

I pinned mine open earlier this morning just to check the temps

 

From my understanding the thermostat comes with a pin in it and is supposed to be pulled out after the tranmission is topped off to ensure the cooling system is completely filled during the checking process at the factory. I actually don't think the service manual says anything about a pin so who knows when or where it was getting removed. Maybe this is why so many trucks came low on ATF

Headed to the lake

 

I pinned the tranny thermostat and hooked up my 14'utility trailer with riding lawnmower and other lawn equipment. I have been right at 190-205ish in town while pulling the trailer. With the factory cooler and no modification other than pinning the thermostat open I never got over 175°. Mostly stayed around 150-160ish depending on the grade. Once I got going over 35-40 mph the temp would fall fairly quick to around 135-145. There is normally a 10-15° difference between the pan reading and torque converter reading. This makes me feel a little better. I just wish I knew what temp the tranny thermostat opens up. I thought about putting a small fan behind the tranny cooler to help it recover faster. It really bugs me that we have mechanical fans and not electronic. I know some people swear by them and say they are more reliable. Just waiting for hot weather here to see what happens with the readings.

 

Thanks for posting this. I have been wondering what those exact results would be myself. After reading a ton about cooler temps for auto transmissions , I wonder why Toyota wants the temp so hot . It seems all they would have to do would be install a 175 degree thermostat and all would be good . I have read that maybe the reason is for better mpgs ? If so this bothers me if they would compromise the life of the trans for better mpg. @gearcruncher . what do you think ?

 

I totally agree with you. I'm going to do some normal driving today to see how it runs without towing. And I wonder why Toyota sets the tranny dash light to come on at 300°.

 

Found this Maybe there is a reason .
https://www.ericthecarguy.com/kunen...d-Here/48131-can-you-over-cool-a-transmission

https://www.bobistheoilguy.com/forums/ubbthreads.php?ubb=showflat&Number=2145553
edit I am thinking maybe it would be best to pin it or add extra cooler just for low speed off roading or heavy towing , when the truck cannot maintain the 195 temps on it's own . I like the op's fan idea for using it when needed . Having the scangauge is really nice to monitor this.

 

In the 2nd pic is that a TEQ sticker? I want 1.

 

Good point and my thinking exactly. So far in town regular driving I have been between 150-175°. I'm thinking the same as you....Pin it open when it is hot or when towing. I would unpin it in cold weather though. I kind of had an epiphany....What if we pinned the factory thermostat open and installed an inline thermostat set to 175-185°. That way you wouldn't have to keep pinning and unpinning. Just an idea.

 

Not a bad idea at all . Where I live it gets hot in summer . A most days in the 90's and over 100 at times . Last year I did not have the scangage. this summer I will watch it and decide if I want to do anything. It worries me to see the trans running at 195 degrees plus when I read all over that 175 degrees is much better for it.
I am sure you have seen charts like the following also .
http://www.txchange.com/heatchrt.htm
Again to the OP , you are spot on with your setup for what you are doing with the truck and where you use it. Great job and write up.

 

Yes. And my understanding is every 20° over 175° your tranny fluid life expectancy is cut in half....SO that means I've driven 7,000 consistently running 190° - 208° thanks to Toyotas tranny thermostat my fluid life is already cut to 50,000 miles.

 

First trip of the season and the bigger cooler worked out great. I left the trans thermostat pinned on the way there. I gave the right pedal hell on a big hill and the pan temp never broke 164°F even though the torque converter shortly spiked up to the 190s.
The T-stat was unpinned for the return trip. The pan temp stayed right about 190°F but the converter temp did climb up to 214°F under load but quickly dropped down to the pan temp when I let off the gas.
I tow in sport mode with ECT on. I do feel like the truck holds 5th gear better with cooler fluid but can't be certain just yet.
I estimate the trailer was about 3500lbs loaded this trip and another 250lbs in the bed of the truck. Ambient temperature was between 68-75°F.

 

I've been trying to find out what the actual degradation table looks like for toyota world standard ATF. I'd really hope 200° is no big deal for it but who knows...