OEM AT Cooler Install
05-13-20, 07:13 AM
#76
Instructor
It is part of the Offroad Package offered in the USA for the 2020 model year.
Why it wasn't offered prior to 2020 model year as part of a tow package is anyone's guess... From a design decision standpoint, if it's not absolutely needed to prevent transmission damage (in the relatively moderate climate of the USA) within the warranty period it's not surprising they cut it out... lower production costs (improve their margin) plus most people who buy a GX do not care if it has a tranny cooler or not in the USA (they're being used to drive to the mall or grocery store).... not offroading or as a primary tow vehicle in the majority of cases.
That being said the new Tundras (and I think Tacomas or 4Runners) in the USA do not have aux coolers either so maybe it was a product line truck/ SUV decision by the North American group not to offer them to the USA market.
Why it wasn't offered prior to 2020 model year as part of a tow package is anyone's guess... From a design decision standpoint, if it's not absolutely needed to prevent transmission damage (in the relatively moderate climate of the USA) within the warranty period it's not surprising they cut it out... lower production costs (improve their margin) plus most people who buy a GX do not care if it has a tranny cooler or not in the USA (they're being used to drive to the mall or grocery store).... not offroading or as a primary tow vehicle in the majority of cases.
That being said the new Tundras (and I think Tacomas or 4Runners) in the USA do not have aux coolers either so maybe it was a product line truck/ SUV decision by the North American group not to offer them to the USA market.
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Acrad (05-13-20)
05-13-20, 07:55 AM
#78
Instructor
With the AT thermostat open (pinned open or naturally open) the AT fluid is routed forward to the built in cooler in front of the radiator (and to this auxiliary cooler if installed) for additional cooling before being returned to the pan.
If the thermostat doesn't open then the fluid cannot be cooled and one would likely get the warning light on the dash fairly quickly indicating the transmission fluid is overheating.
Post #17 of this thread shows the pictures for the 2 different flowpaths (AT thermostat closed and AT thermostat open). Every USA GX has *4 in those pictures, this thread shows how to install *5.
At the end of the day, so long as the thermostat is not pinned open the vehicle will not operate any differently until the AT thermostat (attached to AT warmer by the pan) is opened. Once open, the fluid is directed to the coolers and the fluid will cool down quicker and reach a lower equilibrium temperature since there is additional cooling capacity for the fluid by adding *5. Simple fluid flow and thermodynamics...
Acrad has driven around with his thermostat pinned open to collect some data (this means most likely the AT fluid will warm up slower and take longer to reach a lower equilibrium temperature), not a bad thing to consider in the warmer months and when planning to do some heavy towing (it takes 5 seconds to pin the thermostat open). I have decided not to pin mine open because worry pinning the thermostat open long term may damage the thermostat internal element or prevent it from operating normally if it is ever unpinned (like if traveling to colder climates). Note that by procedure one is instructed to pin it open to properly perform the level check with the vehicle running, so there is surely no danger in pinning it open for short durations during maintenance). Pinning open the thermostat is really a personal preference... I choose not to because I do not tow and prefer the vehicle systems to operate as designed... acrad tows (and over mountains sometimes I think too) so I definitely see the benefit in that specific scenario/ trip of pinning it open.
If the thermostat doesn't open then the fluid cannot be cooled and one would likely get the warning light on the dash fairly quickly indicating the transmission fluid is overheating.
Post #17 of this thread shows the pictures for the 2 different flowpaths (AT thermostat closed and AT thermostat open). Every USA GX has *4 in those pictures, this thread shows how to install *5.
At the end of the day, so long as the thermostat is not pinned open the vehicle will not operate any differently until the AT thermostat (attached to AT warmer by the pan) is opened. Once open, the fluid is directed to the coolers and the fluid will cool down quicker and reach a lower equilibrium temperature since there is additional cooling capacity for the fluid by adding *5. Simple fluid flow and thermodynamics...
Acrad has driven around with his thermostat pinned open to collect some data (this means most likely the AT fluid will warm up slower and take longer to reach a lower equilibrium temperature), not a bad thing to consider in the warmer months and when planning to do some heavy towing (it takes 5 seconds to pin the thermostat open). I have decided not to pin mine open because worry pinning the thermostat open long term may damage the thermostat internal element or prevent it from operating normally if it is ever unpinned (like if traveling to colder climates). Note that by procedure one is instructed to pin it open to properly perform the level check with the vehicle running, so there is surely no danger in pinning it open for short durations during maintenance). Pinning open the thermostat is really a personal preference... I choose not to because I do not tow and prefer the vehicle systems to operate as designed... acrad tows (and over mountains sometimes I think too) so I definitely see the benefit in that specific scenario/ trip of pinning it open.
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Acrad (05-13-20)
05-13-20, 08:01 AM
#79
Super Moderator
Thread Starter
Correct I tow and in mountain passes a lot. Another tip if someone doesn't want to install the cooler is to begin monitoring their AT temps and also add a gauge (you can add this in OBD Fusion/Link) that shows AT torque converter lockup. If you can stay in lockup on a grade temps will generally rise very little and also cool down if it was hot being out of lockup.
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nuclearn8 (05-13-20)
05-13-20, 08:09 AM
#80
Instructor
This is a good point. I wish I would have monitored temps with obd fusion before installing the cooler but alas it is what it is.... if towing a lot I would definitely look into adding a TC lockup kit.
05-14-20, 10:05 AM
#82
Driver School Candidate
need help!
Hi all, just joined this forum seeking help. I own a 2015 GX 460. I live in Colorado and recently purchased a 5500 GVWR travel trailer (probably towing ~5000 lb). I have been monitoring my transmission temps via Fusion and during a short trip up some relatively steep foothills, I have seen temps up to 250F in the torque converter and 235F in the AT oil pan. I am worried how hot I might get on prolonged climbs. I tow at max a couple times a month so maybe the high temperatures are not a big deal, but I obviously don't want to wreck my AT.
Talking to my local Lexus dealer, they are not even aware of the auxiliary cooler option (they say it does not exist!) and advise I do not add anything. They are just telling me to live with it, that I should be fine, but at the same time tell me to try to keep the temperature down. They cannot even tell me at what temp the high temp warning light comes on.
I would happily install the cooler if I could find a place to do it, but am struggling thus far with that. Two transmission shops told me they wont touch it and a third is being very slow to get back with me. So any thoughts on this would be greatly appreciated. FYI, I am not capable of installing this myself.
Talking to my local Lexus dealer, they are not even aware of the auxiliary cooler option (they say it does not exist!) and advise I do not add anything. They are just telling me to live with it, that I should be fine, but at the same time tell me to try to keep the temperature down. They cannot even tell me at what temp the high temp warning light comes on.
I would happily install the cooler if I could find a place to do it, but am struggling thus far with that. Two transmission shops told me they wont touch it and a third is being very slow to get back with me. So any thoughts on this would be greatly appreciated. FYI, I am not capable of installing this myself.
05-14-20, 10:16 AM
#83
Intermediate
I would happily install the cooler if I could find a place to do it, but am struggling thus far with that. Two transmission shops told me they wont touch it and a third is being very slow to get back with me. So any thoughts on this would be greatly appreciated. FYI, I am not capable of installing this myself.
05-14-20, 12:35 PM
#86
Driver School Candidate
Correct I tow and in mountain passes a lot. Another tip if someone doesn't want to install the cooler is to begin monitoring their AT temps and also add a gauge (you can add this in OBD Fusion/Link) that shows AT torque converter lockup. If you can stay in lockup on a grade temps will generally rise very little and also cool down if it was hot being out of lockup.
05-14-20, 12:49 PM
#87
Super Moderator
Thread Starter
I monitor lockup with OBD Fusion or Link (same app - one comes with their adapter). Then through manual gear selection and gas pedal modulation can often keep in lockup which keeps the temps down.
TC Lockup gauge assuming you have the model/year expansion pack loaded
Add a Gauge called "Status of the Lock Up"
Location: PID -> Toyota,Lexus, Scion -> Engine and Electronic Controlled Transmission
Lockup = 1
Unlocked= 0
TC Lockup gauge assuming you have the model/year expansion pack loaded
Add a Gauge called "Status of the Lock Up"
Location: PID -> Toyota,Lexus, Scion -> Engine and Electronic Controlled Transmission
Lockup = 1
Unlocked= 0
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cwalker022 (05-14-20)
05-14-20, 12:51 PM
#88
Driver School Candidate
I monitor lockup with OBD Fusion or Link (same app - one comes with their adapter). Then through manual gear selection and gas pedal modulation can often keep in lockup which keeps the temps down.
TC Lockup gauge assuming you have the model/year expansion pack loaded
Add a Gauge called "Status of the Lock Up"
Location: PID -> Toyota,Lexus, Scion -> Engine and Electronic Controlled Transmission
Lockup = 1
Unlocked= 0
TC Lockup gauge assuming you have the model/year expansion pack loaded
Add a Gauge called "Status of the Lock Up"
Location: PID -> Toyota,Lexus, Scion -> Engine and Electronic Controlled Transmission
Lockup = 1
Unlocked= 0
Very helpful, thank you!
05-22-20, 08:31 AM
#89
Instructor
Was thinking it should be easy enough for us to figure out the thermostat temperature range from starting to open to fully open under normal operation (since it's not listed in any manuals....)
Just go under the vehicle with it idling on ramps (with OBD fusion app up and running) and monitor the Pan Temp while watching the AT thermostat move (the part that the procedure instructs to pin open)... Then we'd know what temperature ranges the normal operation for the AT thermostat correspond with...
put some painter's tape on the end and when it peels off, that's the start of the thermostat opening...
and once you're able to drop in a paper clip or cotter pin, I'd consider that the fully open temp of the thermostat
(this assumes this externally visible portion of the A/T thermostat (which is pinned open for maintenance) is internally attached to the wax element that expand with temperature to change the flow path... it could be not attached depending on the internal design of the wax thermostat)
Just go under the vehicle with it idling on ramps (with OBD fusion app up and running) and monitor the Pan Temp while watching the AT thermostat move (the part that the procedure instructs to pin open)... Then we'd know what temperature ranges the normal operation for the AT thermostat correspond with...
put some painter's tape on the end and when it peels off, that's the start of the thermostat opening...
and once you're able to drop in a paper clip or cotter pin, I'd consider that the fully open temp of the thermostat
(this assumes this externally visible portion of the A/T thermostat (which is pinned open for maintenance) is internally attached to the wax element that expand with temperature to change the flow path... it could be not attached depending on the internal design of the wax thermostat)
Last edited by nuclearn8; 05-22-20 at 09:33 AM.
05-23-20, 07:08 AM
#90
Super Moderator
Thread Starter
On the Tundra forums I've seen reports of anywhere between 190-210°F ....but like you said nothing in official documentation either.