Adding a Trans Cooler, to Fan or not to Fan? (1 Viewer)

[LostLexus]

I've been considering adding a transmission cooler to my 2020 GX, and I'm in a dilemma about whether I should install it with or without an aux fan. On my previous vehicle, a Diesel Ram 2500 I came close to cooking my transmission fluid a bunch of times with the type of wheeling I do. Mostly consisting of slow-going technical trails where there wasn't enough air flow to efficiently cool my transmission and the stock clutch fan wasn't pulling enough CFM. The solution was adding a Derale 15870 Hyper-Cool to the truck and running the aux fan on the trail. Worked great and kept my trans right at normal operating temp. I love my GX and want to keep the transmission as cool and happy as possible, because I plan on owning this thing until the wheels fall off.

I've been following this forum post for a while now (OEM AT Cooler Install - ClubLexus - Lexus Forum Discussion - https://www.clublexus.com/forums/gx-2nd-gen-2010-present/919173-oem-at-cooler-install.html) and decided to install a trans cooler because of the weight added to my GX with larger tires, bumpers, skids, sliders and camping gear. I bought all the OEM parts to make this work besides the cooler, as I would like to install something bigger than the small factory add on cooler.

I plan on installing a cooler on the driver side as the passenger side has the OEM pusher fan on the radiator. Anything worth doing is worth overdoing so I plan to mimic Sandcat's cooler install on his GX460, but only using the Derale cooler (video linked at the bottom) with this unit here (Derale Cooling Products 13700 Derale Electra-Cool Remote Fluid Coolers | Summit Racing - https://www.summitracing.com/parts/der-13700). I have a Victory 4x4 Strike bumper without a winch, so I have a bit of extra room to play with if need be. Another option I was looking at was this smaller unit (Derale Cooling Products 15850 Derale Atomic-Cool Remote Fan-Mounted Oil Coolers | Summit Racing - https://www.summitracing.com/parts/der-15850) that should be able to tuck up right next to the rad if I relocate my horns.

Any input or insight would be greatly appreciated!

 

[Roody]

Following. We've had a bunch of conversations regarding trans coolers lately, and I intend to add one eventually as well.

 

[LostLexus]

Following. We've had a bunch of conversations regarding trans coolers lately, and I intend to add one eventually as well.

Which cooler were you thinking about running?

 

[Roody]

Which cooler were you thinking about running?

Not sure, hadn't pinned down exactly which one yet. @JDUB fab knows the details

 

[Rednexus]

The OEM trans cooler location on these gets pretty good airflow (behind the grille). Typically the coolers with a fan are for use in areas with poor airflow at low speeds. In my experience (albeit on a 470), the trans usually doesn't have heat problems at low speeds. Most of the heat problems are when pulling long grades or towing with the TC unlocked, which is when the GX builds quite a bit of heat, despite having excellent airflow thru the grille. My trans stays cool at low speeds - including in difficult situations like rock crawling, getting into mud, playing in snow, etc - for whatever reasons the A750 at least stays cool when crawling. It stayed cool at low speeds before and after upgrading the cooler.

So there is probably no need to have a fan. A larger $50 cooler like a Hayden 678 should keep your transmission plenty cool. I have the 678 in the OEM location on my 470, and made some simple steel brackets to get it to fit. It's literally 3X the size of the OEM cooler. My trans rarely gets above 200F; when it does I'm usually pulling our camper up very steep grades in 95F plus temps and haven't bothered to lock the TCC. Under normal conditions it typically runs around 80 degrees hotter than ambient temps.

 

[LostLexus]

The OEM trans cooler location on these gets pretty good airflow (behind the grille). Typically the coolers with a fan are for use in areas with poor airflow at low speeds. In my experience (albeit on a 470), the trans usually doesn't have heat problems at low speeds. Most of the heat problems are when pulling long grades or towing with the TC unlocked, which is when the GX builds quite a bit of heat, despite having excellent airflow thru the grille. My trans stays cool at low speeds - including in difficult situations like rock crawling, getting into mud, playing in snow, etc - for whatever reasons the A750 at least stays cool when crawling. It stayed cool at low speeds before and after upgrading the cooler.

So there is probably no need to have a fan. A larger $50 cooler like a Hayden 678 should keep your transmission plenty cool. I have the 678 in the OEM location on my 470, and made some simple steel brackets to get it to fit. It's literally 3X the size of the OEM cooler. My trans rarely gets above 200F; when it does I'm usually pulling our camper up very steep grades in 95F plus temps and haven't bothered to lock the TCC. Under normal conditions it typically runs around 80 degrees hotter than ambient temps.

Awesome, thanks I'll give this a look! Thinking about it more, there is probably a lot more engineering that went into the GX/Prado than my old Ram 2500. You're exactly right about poor air flow at low speeds, that's why I installed the cooler with a fan. The problem I was having was the TC was never locking up generating a ton of heat lugging an 8,000lb+ diesel truck around. One wheeling trip before installing that cooler, my Ram's trans hit 280 after driving a loose up hill 5-mile trail in 4HI. Ouch! The type of wheeling I mostly do is slow-going technical stuff that where all the vehicle's cooling is reliant on the fan clutch. I've only owned my GX for about 6 months now, and it's amazing how much better built it is than my previously owned Mopar vehicles.

 

[JasonW]

Thought the 2020+ came with the factory with the transmission cooler?
I added the factory cooler to my 2018. Just pinned open the thermostat but haven’t drove it yet.

Different vehicle but I installed a B&M Hi Tek cooler, it has a built in fan and temp sensor that makes the fan come on at 175F. Also added a manual override to keep the fan on as needed.

 

[Acrad]

In the US market the external AT cooler was only added as an option to the Luxury trim with the Off-road package for 2020-2023.

It has been optional in markets outside of US since 2010.

Another part I'd recommend even if not going OEM

 

[jdam]

In the US market the external AT cooler was only added as an option to the Luxury trim with the Off-road package for 2020-2023.

It has been optional in markets outside of US since 2010.

Another part I'd recommend even if not going OEM

Saw this in the other thread as well - is this to pass through the radiator core support instead of slipping the hoses through? A little lost as to where they belong.

 

[Acrad]

@jdam

Correct

 

[LostLexus]

In the US market the external AT cooler was only added as an option to the Luxury trim with the Off-road package for 2020-2023.

It has been optional in markets outside of US since 2010.

Another part I'd recommend even if not going OEM

Just had those parts delivered today!

 

[Jetboy]

You should be able to monitor trans temps with a basic ELM327 adapter and torque app. I used that on my 4runner. I never saw extreme high trans temps with or without a cooler. The only time I ever saw them climb above around 220* was on long grades pulling my travel trailer. They'd top out about 230. Off road it was never an issue for me. I did add an aux cooler that was just relying on the OEM fan. It kept the trans temps around 210 max towing. Probably didn't need it, but it was nice for piece of mind. I think you're on the right track to skip the aux fan. No need IMO.

 

[LostLexus]

I decided the route I’m going to take. I’m going with a Hayden 678 or 698 with an internal bypass. Both are priced the same and have the same dimensions. I found a mounting solution that looks really well made for these coolers made by Mountain Passes Off-road.

 

[Roody]

I know design and fabrication is a time-consuming, intricate business, but $175 for the bracket seems extremely steep considering the cooler itself is <$50.

 

[Rednexus]

I know design and fabrication is a time-consuming, intricate business, but $175 for the bracket seems extremely steep considering the cooler itself is <$50.

Agreed....I built one out of scrap steel flat stock in maybe an hour, with a HF welder. It ain't pretty but it works great. That being said, no one else makes these, and there is value in a true bolt-in solution if you aren't set up to DIY fabricate one.

 

[Aonarch]

I just installed the Hayden 678, it was very easy.

I say install the trans cooler first, then use an app like OBDLink with a Bluetooth OBD device to monitor temps.

I am going on a cross country trip in a week and will be wheeling. So I haven't tested my cooler yet, but so far in rush hour traffic, drives, etc my temps have been fine. I have seen guys that wheel heavily install a small Hayden fan, which will definitely help.

For the brackets I just used thin mild steel strips, maybe 2" wide and bent them in my vice, after using CAD (Cardboard aided desing) to mock them up. I then just used M6 bolts with lock washers to fasten it.

 

[LostLexus]

I know design and fabrication is a time-consuming, intricate business, but $175 for the bracket seems extremely steep considering the cooler itself is <$50

It is steep, I have very little free time making it worth having someone else just make it. Plus these brackets look really well made so I know it’ll be able to handle an aux fan if I decide to run one in the future.

 

[HVLA]

I just installed the Hayden 678, it was very easy.

I say install the trans cooler first, then use an app like OBDLink with a Bluetooth OBD device to monitor temps.

I am going on a cross country trip in a week and will be wheeling. So I haven't tested my cooler yet, but so far in rush hour traffic, drives, etc my temps have been fine. I have seen guys that wheel heavily install a small Hayden fan, which will definitely help.

For the brackets I just used thin mild steel strips, maybe 2" wide and bent them in my vice, after using CAD (Cardboard aided desing) to mock them up. I then just used M6 bolts with lock washers to fasten it.

View attachment 3348100

Any close up pics of the bracket?

 

[Aonarch]

Any close up pics of the bracket?

Best I've got.

 

[r2m]

If I were adding a fan, aside from a thermal switch, I may also opt for a manual over-ride switch.