FYI, just had this same cooler installed. Ordered the same part number (32910-60171) from Amayama ($204USD inc. shipping from UAE), however the Denso part number ended in 8861 instead of 8860 as in the photo above. Apart from that the cooler looked identical and fit as OEM.

 

Many thanks to all whom have contributed to this thread, as it has helped guide me down the path of an aux trans cooler install which I consider to be mandatory if you tow with the GX. On my previous GX470 I upgraded the OEM trans cooler to the Hayden 678 because I still wasn't happy with trans temps when loaded up with family and towing a 4500lb camper, and it proved to be a good choice.

While I would have preferred to keep an OEM setup for the simplicity and proven fit and finish, I figured it would just put me in the same place I was with the GX470 wanting to upgrade to the larger cooler, so I decided to do a hybrid setup of OEM transmission hoses and an aftermarket cooler.

I will note that if you are going aftermarket with the cooler, the metal hard lines running through the bulkhead shown below have nothing to bolt to, as the would typically bolt to one of the OEM trans cooler mounts. I would suggest that you buy the oem mount 32913-60260 as it has indexing/alignment tabs that would be more reliable then a custom bracket. For now I fab'd a custom bracket, but I plan to order the oem one and cut the trans cooler mount off.

 

Got her all buttoned up yesterday with the Hayden 678 cooler and last night went for a test drive to check for leaks. Did a few hard launches from stops and on ramps, and after it was good and warmed up cruising at 70mph (ambient temps 67*) saw temps were basically the same as before adding the cooler at 190ish pan temp, with torque converter temps reaching over 200*.

To my uneducated mind (aka I really don't know what temps this transmission likes) those temps seem high. So I went home and pinned the thermostat open, and went for another drive. Did the same drive with hard launches and cruising at 70mph and temps were 160deg. Which leads me to believe that the engineers designed the thermostat to open at higher temps then most people seem comfortable with (myself included). My guess is the engineers found 190deg range is the happy spot for this transmission.

The GX is a 2017 w/ just shy of 60k miles on it, and I'm scheduled for a complete fluid exchange Saturday which will ensure good base line numbers and correct fluid levels. Once that is done I will follow up with more testing. We do have a few more camping trips lined up as well, which will really tell the story on the external cooler performance, as I really wasn't comfortable with the temps when towing.

 

I’ve had my AT thermostat pinned open for years now.

 

For what reason though? Not at all being a **** because you have provided a ton of useful info here and this is just a general question not really aimed at any certain person, but as an engineer myself I look at how many A460's are out there and how few have issues, and think that maybe the Aisin and Toyota boys know their stuff? I mean if the "severe use intervals" apply to you then I can see the need for a few upgrades to ensure longevity, but for the majority of the folks that doesn't apply. I would imagine that transmissions have an optimal temp window as well, and by pinning the thermostat you are operating at colder then ideal temps for longer periods of time, which isn't ideal.

 

It is common practice noted on the Tundra forums and has allowed me to at least keep temps aligned with coolant and with lower peaks than if I let the AT thermostat open.

I never noticed a difference in shifting quality or MPG decrease even when the temps turned cold. It still has the coolant feed to warm things up albeit at possibly a slower rate.

I can only speculate long term frequent AT fluid maintenance and attempts to keep fluid temps low will result in increased longevity of transmission on my vehicle.

There are some AT failures in thread here and on IH8Mud. These have generally been in the 150K+ mileage category.

Is it more or less just the fluid schedule, hot temps, or both? Time will tell.. consider me the long term experiment of any adverse effects with it pinned open. :-)

So far haven’t felt a need to go with bigger cooler but will monitor trends again with heavier trailer loads.

IMO: Higher temp specs have been done for CAFE and/or emission standards to get up to temp as quickly as possible.

 

Example from 2022 Warranty Services Guide

As for severe use this can be far beyond towing a trailer.

- Fully loaded with passengers and gear

- Cargo box on the roof

- Extended idling in the city or slow driving on/off-road

 

So I took my 2017 to Toyota service for a trans fluid exchange. I printed off the fluid level inspection procedure from the FSM you had posted here because I do understand the tech might not have access to the correct software for the GX, put it on the passenger seat right under the donuts I bought for him, and in black magic marker wrote "for reference" on it.

Well I was closing my tab with the service advisor when the tech walked in, and I had asked him about how it went and he did describe the procedure and how the machine replaced the exact amount removed based on weight. I did ask if he performed the fluid level check outlined in the FSM, and he said he didn't think he needed to because the machine handled it. Well, how do you account for the extra volume required from the external cooler I made sure the service advisor noted in description of work, and how do you know the level was correct prior to the service?

He went and grabbed the packet I had printed and looked through it, and what I found interesting is a 15+ year master tech at Toyota acted like he had never correctly done this procedure on any vehicle he worked on based on how he described his usual checking procedure. Well, long story short he didn't have any issue pulling it back in and checking the level using techstream.

My testing before and after the fluid exchange shows normal operating temps are indeed right around 190ish (ambient 65-67deg), but I did note that it appeared as if the trans fluid did take a bit longer to hit the 190deg range after the fluid exchange. We will be towing back to back weekends starting the first weekend in Oct, and hopefully the trans cooler will have a positive affect.

 

yes. ive seen techs learn from others an incorrect method. they just figure since bob has been there doing this 20 years he must be correct. they never wonder if bob has been doing things incorrectly from the beginning. because bob learned from someone else that was around before the improved process. that was joe. joe figured he'd been doing things this way for 15 years without complaints that he didnt need to learn the new method.

 

First tow with the trans cooler and after the trans fluid exchange, and the transmission is certainly more happy with the trans cooler. Once up to temp and cruising on the interstate at 70mph (48* deg ambient), it never came off 196.3*. So my guess is that 195 is when thermostat opens.

 

So... just curious... after the tech pulled your GX back in to the shop, did it turn out that the fluid level was indeed correct, over-filled, or under-filled?

 

I was very curious about that as well, but he said before he even checked the level he just added 1.5qrts to the system, and when he removed the inspection plug a bunch drained out. But yes it should be a little low based on the extra volume from the added lines and trans cooler. I remember my GX470 being very sensetive to fluid level, and having it be low from a engine radiator change was enough to increase temps by 20-30 degrees just during normal driving.

My tow home on the interstate yesterday at 54deg ambient produced excellent numbers again. The trans pan never rose above 195*. With the Michelin Defender LTX m/s inflated to max 44 psi and the hayden cooler, I now consider the GX ready for duty!

 

Has anyone added this to the equation? Curious to know how well this performs. I bought one last October and will find out this spring when it's installed.

https://csfrace.com/new-csf-lexus-gx...inum-radiator/
From their site:

Quote:

"Additionally, the radiator features a built-in transmission oil cooler. The transmission cooler is a heavy-duty high-performance 5 plate design that connects to the OEM hoses. The upgraded built in cooler is great dealing with the added heat and stress from towing, low gear crawling, and vehicles equipped with oversized tires. While many understand the impacts of oversized tires, it is always good to provide extra incite. By increasing the diameter of your tires, you are reducing the effective gear ratio. This means the engine and transmission have to work harder to move the tires. Obviously this will end up generating excess heat, but the CSF radiator is designed to handle it."

 

My guess as well is that is pretty accurate. It will be a few more weeks before I start towing but last Saturday drove 75 miles to a club to pick up half a ton of lead shot for reloading shotgun shells. Ambient air temp was 28° to 30° and tranny sump and TC temps held at 195° pretty solid on the way to the club. Loaded up with the lead on the way home it would rise some on the hills but drop back down to 195°-200° I was impressed. Until I got to the long hill going up to my house. TC hit rose and hit 238° pretty fast and didn't want to drop until I got home. The sump temp was climbing slowly and trying to catch up with the TC. Why I am looking at an aux trans cooler.

From a previous post you made pretty sure we are not that far apart from each other. Do you cover, at least partially, your trans cooler in the winter? I'm going back and forth between the 678 and 698. Wanted to avoid the hassle of blocking the 678 in the winter, pretty sure that would be a requirement where we live. On the other hand the reviews on the 698 with the built in bypass seem to be hit or miss especially on maintaining steady temps. Not sure yet which way I am going to go. With the exception that I need to get the transmission temps down once I start towing or under load.

 

Well hurry up and install it and report back already! LOL. I ran across that last night when digging around for cooling solutions. My 19 Lux only has 42K on it so a bit soon to be replacing the radiator but if it had another 20-30K on it would consider trying that one. Wish they had BTU ratings for it. One of the first things that hit me was that they don't mention the transmission warmer that many have mentioned that exist in the radiator. So looked at the OEM rad and didn't really find anything from the factory diagrams or searching around. I really need to break down and get the FSM.

Going off repair and parts diagrams, so not as good as the tech manual, the thermostat for the transmission fluid is circled in blue



The item circled in red looked like a heat exchanger to me so looked it up and is listed as AUTOMATIC TRANSMISSION OIL COOLER Part Number: 3349334030



Not uncommon to see a heat exchanger listed as a cooler instead of warmer.

So going to go with that is the transmission warmer and it is not in the radiator, the radiator just provides the heat for it and the transmission thermostat controls the flow. And the flow to the transmission fluid cooler built into the radiator.

Which means the CSF should be fine even in cold climates. Not sure how much more cooling it provides for the transmission fluid over the factory radiator but I'm curious and would think it MAY be more. Then again Tech Writers like to call warmers coolers and any Ad Writer or content creator worth their pay check will make anything sound good.