Transmission temps on a Gen 3 Tundra

We just bought a 2016 Tundra, trading in our 2014 Tacoma. Pretty disappointed in transmission temps on the new Tundra, and we haven't even towed yet. Temps just driving around town or cruising on the freeway run from 185-220*. Those are unacceptable temps for towing, not to mention just driving around. I appears the transmission has two systems for temp control of the trans. One is back at the tail of the trans, where engine coolant is used to control temps on the trans. Also, it appears the transmission lines run up to the A/C condenser, perhaps being used for both the A/C and the trans. The biggest problem I see with the system after a brief look is the use of engine coolant for temp control. If those lines are not controlled with a thermostat, hot coolant, 190-212* will be heating the trans fluid to that temp. So no cooling of the fluid will start until the trans fluid temp exceeds the water temp. Does anyone know if the water lines to this heat exchanger are controlled by a separate thermostat? Secondly I question how efficient the A/C condenser that shares double duty with the transmission is at cooling. The temp differential between the transmission torque converter, the hottest temp sensor to the pan temp sensor is about 15-20 degrees. My 2014 Tacoma had a large B & M cooler I put on it and the temp differential with it at those two points was 25-33*. So all in all I'm disappointed in this system. Does anyone on the forum work as a Tundra Mechanic, and can you enlighten us on this system? Has anyone put a supplemental cooler on their Gen 3 Tundra? Has anyone disconnected the engine coolant portion of the system and seen improvement of heat reduction? And finally, what kind of transmission temps are people seeing towing heavy, i.e in excess of 7000 lbs? Thanks guys!

 

First I'll admit I've never looked under a Tundra.

But I've never seen anything like you describe either.

Transmission coolant lines typically run from the transmission to the bottom of the radiator. The radiator fluid and transmission fluid do not mix, but the trans fluid is cooled by air flow from driving and fan, just like engine coolant. No tstat control on the trans side of things, just continual pumping.

I'm thinking you are describing a factory transmission cooler, mounted in the area of the condenser, but of course they can't be part of the condenser in any way. So on a tow package, you have a separate 'radiator' or 'cooler' for the trans.

What is it that gives the trans temp readings. I've also never seen this from the factory. In fact, they quit using real coolant temp gauges decades ago because people got so flustered. Hence 'idiot lights'.

 

Clearwater, I'm getting my trans temps from my Scan guage. As for the other observations, I have traced the lines, and as odd as it may sound, what I describe is fact. Using water to contol temps on an auto trans is nothing new. The Tacoma had a line run thru the radiator, and it is common on many transmissions. As for what appears to to be the A/C condenser sharing duties with the trans I've never seen, but that is how the lines trace out.

 

I agree with Clearwater .
Something very weird going on with your Tundy .
Keep in mind that normal operating temps for your transmission are about 180 degrees .
With that said your engine coolant warms your transmission up first thing in the am .
Maybe a larger cooler for your trans is needed . I usually recomend the TRUE COOL 4490 for the Tacoma , but it would also work just fine on a Tundra .
Lets have a peek at what transmission coolers do
TRANSMISSION COOLERS
If you do not have a transmission cooler on your truck and you plan to tow or haul heavy loads or you are in heavy stop and go traffic and use 4X4 low a lot , consider purchasing a cooler . The cooler thats built into your rad is designed to cool the transmission with the weight of just the truck by itself .When you are in 4x4 low , your torque converter is usually in the stall stage and creates a tonne of additional heat .You dont have much air flow going through your rad when you are in low range 4x4 .
160 - 200 are considered normal temps providing your engine radiator is functioning properly . If your engine overheats , your transmission will also overheat
Normal fluid temperature in transmission to be 175 deg. F.

Rate of oxidation to double for each temperature increase of 20 deg F above normal (175 deg F). As oxidation rate doubles, useful life of fluid is cut in half.

At 175 deg F life is 100,000 miles
At 195 deg F (20 deg above 175) life is 50k miles
At 215 life is 25k miles
At 235 life is 12k
At 255 life is 6,250
At 275 life is 3,000
At 295 life is 1500
At 315 life is 750

At temperatures much above 300 deg F the metals in the transmission will tend to warp, twist etc. high temperatures causes the formation of varnish deposits which impair or pre vent transmission operation.

At a fluid temperature of 415 deg F fluid life is 30 minutes!

Source: Empire Lubricants Inc.
Consider a scan guage http://www.amazon.com/ScanGauge-Comp.../dp/B000AAMY86
Here is the best information for the scan guage http://www.tacomaworld.com/forum/2nd...-pressure.html

Ultraguage is now offering transmission temps http://www.tacomaworld.com/forum/2nd-gen-tacomas/318340-ultragauge-transmission-temp.html

You could also use the Torque app with an Android phone as a cheap alternative to watch your temps http://www.tacomaworld.com/forum/per...d2-reader.html

This is how Low Pressure Drop technology works::
When Automatic Transmission Fluid (ATF) is cold it is viscous. The unique Tru-Cool design allows the colder, thicker ATF to flow more efficiently through two open bypass channels positioned at the top of the cooler. As operating temperatures increase, the ATF becomes hotter and thinner, It's then directed through the core where it is cooled. Tru-Cool's highly efficient cooling technology combines improved protection against lube failure with optimal heat transfer.
http://www.amazon.com/Long-Tru-Cool-.../dp/B005XZXB1M
Long Tru-Cool Oil Coolers offer advanced cooling protection for many towing applications. The advanced technology out performs TUBE & FIN Designs, Delivers up to 15 times less flow restrictions, 30% more cooling delivers maximum heat transfer, Self-Regulating for maximum lube flow protection through start-up, varied temperatures and driving conditions, heavy loads and towing.
Here is Toyotas fluid flow guide ...Look at page 8 on this PDF http://www.toyotatundraforum.com/pdf/A750E.pdf
And here is a guy who recently installed a cooler correctly http://www.tacomaworld.com/forum/1st...agram-pic.html

cooler and fan install http://www.tacomaworld.com/forum/2nd...n-install.html

 

Thanks for the reply gearcruncher. I already have a Scan Gauge II, which I mentioned above. That is where I'm getting my temp data. Below is just one of MANY threads on several Tundra sites that all say the same thing. The Gen 2 and Gen 3, (mechanically mostly the same) have a problem with tranny temps. The normal unladen tranny temp is around 200*. The cooling system for the tranny is with engine coolant and that system is located near the tail shaft of the tranny on the passenger side. Also, there are transmission lines that run from that location to the passenger side of the A/C condenser. On the driver side of the A/C condenser is the plumbing attachments for the A/C. So, it appears the A/C condenser unit is plumbed for double duty. As weird as that is, it isn't my concern at this point. On my Tacoma, I put a B & M Supercooler on it and was able to keep my temps in what I would consider normal, usable range, 180-210*.....with the factory cooler it ran at the high end of 230 towing on a steep grades. So, I'm not a newbie to this issue of trans temps, only a newbie on the Tundra. And there is zero wrong with my Tundra. This temp issue is with all the Gen 2 and Gen 3 Tundras out there, but unlike Tacoma guys, the Tundra guys tend to be less gearheads and really are unaware of this tranny temp problem. I miss all the great data I got for my Tacoma from Tacoma World....especially when I'm having this problem.

I know I can delete the engine coolant/trans oil heat exchanger rather easily. And I can put a B & M Supercooler in between the trans and the goofy A/C condenser cooler and likely get my temps down. But I posted to see if the great minds here on TW in the Tundra section can lay some of their brilliance on me....so far it is kind of dark ;-) You have shined a little light on the subject.

Thanks for the PDFs and the time you took to help with all the links and all....the PDF on the fluid flow shows much of what I'm talking about and they even say the ATF temps ARE KEPT HIGHER THAN NORMAL (WITHIN LIMITS) to improve fuel economy. This is on page 8. So there is the reason Tundra run hot, now how to cool it down.

Wish I could find a service manual for this, perhaps I will have to settle for a Haynes Gen 2 manual. I need basic info like torque specs on simple things like oil drain pan, filter housing torques, etc. Most of the Tundra sites don't even have this info. Like I said, getting good info from TW has spoiled me.

Thanks again, hopefully I can find someone who has been there and done that before I try to reinvent the wheel. Here is confirmation that the trans cooler and the A/C condenser share a cooling unit....so I'm not going crazy, ;-)

http://www.tundratalk.net/forums/tundra-drivetrain/119989-where-my-transmission-cooler-located.html

 

With the help of Gearcruncher and the PDF he posted, most of my questions are answered. ONE question remains, that question is:

At what temp does the themostat in the transmission lift to allow hot transmission fluid to go to the transmission cooler? If you have a document or a link to the data it would be appreciated. Thanks!

 

What transmission do you have ? I believe it should be the AB60 series ?
I dont think you will find an answer for your question but if I was Toyota , I would open the trans thermostat at 180 degrees

http://www.ukrtrans.biz/files/2011/10/Toyota_AB60_Transmission.pdf

 

Thanks for the info....I need to check the tag on the tranny to determine the actual model. I did a pull with my travel trailer today as a test. Trans temp stayed at 197* until I started the 7% grade. Then the temps spiked to 226* before I backed off and headed home. This was pulling in S4 at only 55mph, which is a non-overdrive gear and the tranny locks in S4. The temps would have continued up if I hadn't stopped, to where who knows. I've decided to bypass the coolant heat exchanger. That should drop temps by 20-30 degrees. Now I need to know when the thermostat lifts. I agree with you gearcruncher, I would have it lift at 180* But I bet it is 200* or more. If you get more data I would love to see it. But thanks again for the help. I will post as this project continues with how mods are helping or not....

 

So the saga of high tranny temps likely is over. I haven't towed yet, but normal driving the temps are down 30-35 degrees now. The secret is to pin the tranny thermostat open. During a check to inspect the tranny fluid level, part of the procedure is to pin the thermostat open. Once I had done the fluid level check, and based on one of the diagrams gearcruncher provided, I decided to drive with the thermostat open. I believe it will be the fix. Like I said tranny temps dropped 30-35 degrees and coolant temps dropped 4-6 degrees. Once I tow the real test data will be in and I will post here. Thanks again gearcruncher, you provided enough technical documentation to get here. It's nice to have a truck that can pull like it should without damaging temps.....oh, yes to pin the thermostat open take a wire about the size of a paper clip. So when temps drop, or as needed it takes all of 30 seconds to install or remove the pin.....

 

I like your quick fix !!!!
The cooler that critter runs , the better off you are

 

In case anyone is interested in pinning their thermostat to reduce your tranny temps, here is a link to a short DIY write-up I did over at the Tundras site.

https://www.tundras.com/threads/transmission-temperatures.3236/

 

Sounds like I need to upgrade my old Ultragauge to the newer EM for the tranny temp. I didn't realize it would go that hot.

Easy fix for summertime use though. 30 seconds to change it.