Mishimoto Tacoma Transmission Cooler install on Land Cruiser

[GR8Santini]

Good video showing transm temps on prior gen 4Runner & effect of a supplemental cooler.

 

[Bad1975]

If anyone is concerned about longer periods to reach operating temp, Wholesale automatics (transmission experts out of Australia speaks about this in some of their videos.

Something along the lines of in all their years of transmission servicing, repair and developing and fitting valve bodies and improved solenoids and fitting coolers, they've never seen a failed transmission come through their shop because it ran too cool, but have seen plenty killed by heat come through.

Hopefully they will develop a KO clutch lockup kit for this transmission! I'm not holding my breath though as that would take a lot of engineering vs. just replacing a shift solenoid and a modified valve body to force torque convertor lockup in the desired gears. One would need to keep the vehicle in ICE mode only, while disabling regen braking and hybrid drive to allow it's safe use on the KO clutch, maybe they could tie into Tow/Haul to accomplish some of it? Likely not cheap either!

 

[grandsons]

We really need to stop relying on vague marketing and making assumptions (which is exactly what I did), that's why I posted here asking people to monitor their temps properly, just raising some awareness.

Thank you, I also noted on the Max cooler warning. I'd assumed the Tru-Cool 4454 included a thermostatic bypass of some kind, both for warm-up and cold-weather protection, given it's not a Max unit. Maybe a wrong assumption. I'll flag it and get an OBD scanner to monitor ATF temps properly.

But the next question is what is an acceptable ATF temperature?

Are these ranges fine?

-Normal operating temp: 80–100°C (175–210°F) — where you want to be for most driving
-Acceptable upper limit: up to 110°C (230°F) for short periods, towing, or hard use
-Warning zone: 110–130°C (230–265°F) — fluid degrades faster, worth backing off
-Danger zone: above 130°C (265°F) — fluid breaks down rapidly, seals at risk

Cold side is less discussed but also relevant given Swiss winters, running fluid through the cooler before it's above ~60–70°C (140–160°F) is also not ideal, which is exactly why the bypass valve conversation matters.