Transmission cooler for automatic

G'day Craig.
Although the theoretical capacity is 3.5t, that is the max and probably 75% of that is the realistic value. It will move that weight along a road but isn't practical for all situations.
Any weight increase creates more temp within the torque converter and many times, except extremely favourable conditions, the auto will often be operating NOT in LOCKUP mode and so the TC is developing additional heat into the fluid. That will of course elevate the auto fluid temperature. IUA will probably not endorse the fitting of a trans cooler, even though on a hot day, up hill, with a tail wind and towing 2.7T the auto trans will heat up significantly.
Any additional fluid heat is delivered straight to the radiator water heat exchanger, so any additional heat stresses the radiators ability to cool not only the engine but the trans as well.
I would definitely fit one and even have a temp sensor controlled OR manual switched fan assisted cooling airflow for the trans cooler. A great addition is a scan gauge or similar device plugged into the OBD port to read and display auto fluid temp. That way you can monitor the auto temp, sort of. Keep in mind, the temp indicated is ONLY the fluid inside the auto trans and NOT the hotter exit temp of the fluid which is sent to the radiator heat exchanger. Any heat dissipated by a trans cooler is heat which is NOT added to the water cooling system, ONLY IF the trans cooler is placed in the exit HOTTEST line from the auto to the radiator. Cooler in the coolest line still ADDS auto fluid heat to the radiator first. Which is Not my idea of cooling if ever in hot climates or harsh conditions are experienced.
If your vehicle ever gets to warning you or goes into limp mode, the auto has been very hot.
Aisin autos are usually very good, so you should not have problems if not abused by negative usage or heat. Heat will kill any auto.

craig.

The current Dmax and BT50 are essentially the same vehicle, and I have the BT50 version.

These vehicles are NOT fitted with a heat exchanger within the engine radiator, but WITH a heat exchanger that is located beside the Bell Housing, and is cooled/heated by controlled temp engine coolant (ie coolant circulating from the top of the engine (hot coolant) and returning to water pump). This system ensures that the transmission WILL warm up regardless of ambient temperature, whereas the old in radiator system could keep transmission temps very low in freezing ambient temps.

I operated my vehicle for several weeks paying close attention of both engine and transmission temps under a variety of operating conditions, but not towing, and the normal operating temp for the engine is 87 deg. with the transmission always just a few degrees either side of that (measured using Scangauge 11)

I then fitted a cooler before any towing duties and still find those temps are maintained, even when put to the test towing 3t up Cunninghams Gap between Aratula and Warwick SE Qld in February, a 9km climb speed restricted to 60 and 80kph.

It has been fitted to the hot line out of the transmission (which just happens to be the easiest line to access at the heat exchanger) and returns via the heat exchanger to the transmission. This system has NOT seen any appreciable drop in transmission temp, BUT it sees little to no increase in either engine or transmission temps when towing and working hard.

I mentioned this to my Dealer's Service Manager and his reply was "that it is a good thing and can have no adverse effect on the transmission".

It would appear to me that the trend by vehicle manufacturers is to now control the 'warm up' of their transmissions, whilst also preventing them getting too hot. The addition of a cooler as I have it fitted still causes the transmission to attain the manufacturer's desired operating temperature within a few degrees, whilst at the same time dissipating, or taking care of, the additional heat load from the entire cooling system when being asked to work hard.

Manufacturers have gone to low viscosity oils so that it 'squeezes out' from the clutch packs, and they are also now ensuring that the transmission warms sufficiently to also assist that oil to escape the clutch packs to reduce slippage at the gear change points, but it is also good to ensure that the transmission (or any machinery) does not overheat.

Hope this is of assistance.
Athol

Craig, I have been towing our 2,500kg van since 2014 and have towed about 50,000km.

I fitted a Scangauge11 back in 2015 and have seen the ATF climb to 115c on a few occasions, the last time was towing between Kalbarri and Carnarvon with an outside temperature of 44c and a strong tail wind so not much air flowing through the radiator. It got hot enough for the ECU to shut down the air-conditioning. Within weeks of getting home I finally had another cooler fitted by my dealer, Major Motors in Bibra Lake WA.

Pre install I was seeing the ATF temp about 10c higher than the coolant, it now is normally sitting about 10c below the coolant so has dropped the temperature by 20c.

We recently did a 10,000k trip and never had the ATF reach as high as the coolant at all.

I have been lucky with Major Motors as they have never faultered with warranty, they suggested I do a GVM upgrade pre purchase and when I asked for the cooler, they just did it without any questions or claims of it voiding my warranty.

If you are having problems with your dealer, it's time to find one that will support you.

Hello Craig, because I tow, a transmission cooler is the very first accessory I purchase for my car. That and a scangauge. I wouldn’t be without one as they make a huge difference. My car, Hilux, transmission normally runs about 20 degrees cooler than car and with heavy towing only gets to about 90. In your case, being a new car, you would have to make double sure fitting one does not void any warranties?
As for fitting, (while others won’t agree) it should be on the return line after the car radiator and the best and most efficient and effective orientation to mount a cooler, is flow into the cooler at the bottom and out at the top. Some kits you buy are orientated different and I highly recommend rotating them to get the best performance.
I could give you a number of links that explain the reasoning of all this, however at the moment I can’t get links to work, but I’m sure I be adding some long links later to justify myself. lol. Tony

Craig,
Just a slight variation of topic.
Out of curiosity, What is the suggested service life of the tranny fluid by Isuzu?

Another possible solution is to fit a transmission lock-up kit if they are available for the vehicle. A Google search does find one. Perhaps you can get more info on a Iszu dedicated forum. There are some pretty sophisticated kits available for Aisin transmissions but for others?

These people have an excellent reputation for their cooler kits, I have one in my Amarok.
I didn't drill any deeper as I don't which model DMax you have.

See: DMax auto kits