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Here's some data I collected the other week while traveling through NM and Arizona. This is a stock GX460 pulling a bit over 3000 lbs over a 100 mile stretch, climbing ~ 7000 feet, and with a starting ambient temp of 111* in Scottsdale. Highway speeds for the most part. I have no aux transmission cooler, but given these numbers and what I've seen posted for temp reductions I wish I would have had one installed on mine.
1. Cruising across New Mexico's rolling hills with a headwind. No trailer. Ambient temps in the 80's. Similar numbers around Scottsdale with 100* temps.
2. Between Scottsdale and Payson with ambient temps > 100 degress and a 3000lb trailer. This was after a sustained pull for over 5 minutes of steady climbing at pretty steep grades. The measurement was near the maximum for the pan temperature. Torque converter temps actually spiked over 250* a couple of times.
3. Shorter climb just past Payson. Elevation ~ 5000 to 6000 ft.
4. Leveling out at 6000 feet. This is representative of my moving averages pulling the trailer.
As stated, the high point in the AT pan was ~ 242*, and the torque converter temp was ~ 252*. I'm not sure what the settings are for the warning light on the dash (maybe 270ish?) but nothing was triggered. One thing I observed is the "sliding scale" between the engine temps and the AT temps when climbing. Downshifting and holding a gear (like 3rd or 4th), you will see the AT temps drop and level off while the engine revs higher. To me it's a better option to keep the revs in the engine up rather than overworking the transmission in a higher gear, or letting it shift back and forth.
I posted this over in AT cooler thread but might be missed by some
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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
He did say it was over 100 degrees out so those temps are not surprising. I don't think the AT fluid (oem, Amsoil, etc...) makes one bit of difference with regards to the temperature that one would see in the pan or TC.....it's just freaking hot!
The only thing that could help would be an aux cooler in this situation....
Step 1, install a cooler to try and keep the temps as low as possible during all scenarios
Step 2: I firmly believe refreshing the AT fluid (with drain and fills) is a good idea at a more frequent interval than the manual requires
If these 2 things are done then you're doing all you can to protect the transmission from long term issues (unless of course you can change your driving habits to keep the TC in lockup or install the TC lockup kit when towing, then this would also help more than not)
We have a couple triple digits days coming up here in Tejas so I'll go pull some temps while cruising on the flatlands and post up the results
Is your better fluid really allowing you to run cooler under heavy loads without additional cooling? That would be mighty impressive, fill us in please
Not that often - hence my motivation to post here. I drive all over Colorado, but its never that hot here, nor do we really have the kind of sustained, steep, high speed hill climbing that the drive up between Scottsdale and Payson/Forest Lakes offers.
I posted this over in AT cooler thread but might be missed by some
======================================
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
Is the PID "Status of the TC and TE1", "Status of the TCV", or something else?
I'm running temps generally lower than 230F with a 4600# loaded trailer in 90-100F weather in mountainous terrain, but under normal driving it's regularly above 200F; weird.
Last edited by Ontario102; 06-12-20 at 12:51 PM.
Reason: Found answer
The OBDLink app has a really good set of PID's for the GX. I don't have an android phone anymore and started using it when I picked up an OBDLink MX+ adapter that I could use for making FORSCAN edits on my F150. The list of PID's is huge and can see most modules in the GX.
I kinda wonder why the programmed the transmission to unlock the TC so often, that has to be why the ATF temps get so high.
I have been towing about 4200 lbs. and seeing similar trans temps as Jacket, ~180-200 on flat freeway and one mountain pass I drive through it will spike as high as 240. Using the Fusion app and I'll add the TC lockup before I tow again this Saturday. Isn't there some kind of trans cooler thermostat that can be pinned open? Would that be worth doing?
I have been towing about 4200 lbs. and seeing similar trans temps as Jacket, ~180-200 on flat freeway and one mountain pass I drive through it will spike as high as 240. Using the Fusion app and I'll add the TC lockup before I tow again this Saturday. Isn't there some kind of trans cooler thermostat that can be pinned open? Would that be worth doing?
According to several factory technical documents readily found on-line the Aisin manufactured A760F fitted to the Lexus GX 460 employs two temperature sensors (see photo below), each with a different function:
- ATF Temperature Sensor No. 1 (aka TFT1 or THO1) is used by the transmission’s ECM to modify the application of hydraulic pressure control of the clutches and brakes (if it fails 5th and 6th gear up-shifts and lock-up are prohibited). This helps to ensure shift quality. In the attached photo ATM Temperature Sensor No. 1 is the element with the orange wires.
- ATF Temperature Sensor No. 2 (aka TFT2 or THO2) is used by the ECM for shift timing control when the ATF temperature is high. ATF temperature sensor No. 2 (THO2) is used as a basis for modifying the ECT shift timing control when ATF temperature is high. It is also used to activate the ATF temperature warning light on the dash. In the attached photo ATF Temperature Sensor No. 2 is the element with the blue wires.
I have read on this forum (as well as in the Tundra and Tacoma forums) that there are sensors providing fluid pan and torque converter temperatures. The technical references I have read make no mention of this. In addition, I have a ScanGauge2 and only one of the four available x-gauges provides data. Can someone please explain to me where they are getting pan and torque converter temperature readings from?
06-11-20, 11:00 AM
