One of the hallmarks of the Toyota Tundra, for its fans and consumers, has been reliability especially with the stories of the million mile trucks. With a powertrain, and the overall truck, having been largely untouched since 2007, the idea is all the kinks have been worked out. However, a relatively unnoticed change, the removal of the transmission oil cooler, has caused a huge uproar, and irate owners are even talking about a class-action lawsuit.
Starting in the 2019 model year and extending into 2020, Toyota Tundra and Sequoia vehicles saw the removal of the transmission oil cooler. This external cooler is designed to reduce the heat in the transmission, which can lead to catastrophic part failures.
How much heat? The conventional wisdom for years has been it should be less than 200 degrees when empty and below 225 degrees when towing (between 175 and 225). Anything higher than these numbers can cause the fluid to break down and seals as well as parts to fail.
Owners tracking temps
Over the course of the last few months, we have had several owners come forward with stories of their trucks running higher transmission temperatures than they would like. Doing more investigation, we discovered the transmission oil cooler was missing.
One of the affected owners went from a 2017 Tundra to a 2020 Tundra and proceeded to tow the same load as he did before. Now, his 2020 Toyota Tundra is throwing error codes at him for overheating.
As he looked into the issue, he discovered the transmission was operating a little higher than 220 degrees empty and presumably climbing much higher towing. While he hasn’t used his phone app with the OBD2 sensors to track temperatures when towing, he has dealt with a persistent issue of a high transmission temperature warning on the dash.
He believes this happens when the transmission surpasses 304 degrees.
He has had the truck checked out by the dealer and has since ordered a new ATF cooler to install on his truck like another owner.
The other owner, who goes by DirtE30 on YouTube, has not only documented his issues but also created a series of videos on how to install an ATF fluid cooler as well as how his fluid looked after 40,000 miles (before switching to Valvoline Maxlife ATF fluid, more on this further down). It is an interesting watch and you can see his temperatures dropping 10-20 degrees after installing the cooler.
Finally, the big issue for a lot of owners is the feeling of being misled. The sales stickers (aka Monroney labels) for the Tundra and Sequoia haven’t been changed to show the transmission oil cooler is no longer installed. This scan of the sticker shows the transmission oil cooler on it under the tow package. It’s a bit blurry, so we are working on getting a new one.
This has lead many owners to discuss calling an attorney, filing a class-action lawsuit or other such action to force Toyota to install the transmission oil coolers since it was listed on the sticker.
Toyota responds claiming all is fine
We reached out to Toyota on this issue and they said in separate conversations and interviews, the truck’s transmission was operating as it should. Plus, in the case, of the owner with the overheating transmission message, it is likely a sensor issue causing the error code to be thrown (the owner tells us, he has had his truck checked out by the dealer and the dealer can’t find anything wrong).
Why are the temps higher in the first place? Toyota says the higher temps are just a byproduct of new synthetic automatic transmission fluid allowing them to run hotter than conventional oil. The chart above is based on old conventional oil and as such is outdated in their view.
There is some merit to this statement. For years, Toyota “WS” is/was the transmission fluid used in their vehicles. So, what is the WS, and who makes it? Well, those are trade secrets long used by all automakers to ensure consumers use their products.
While, we can’t narrow down exactly what that fluid is or if they have changed it like they claim to a synthetic oil, we can compare it to the leading alternative transmission synthetic fluid called the Valvoline Maxlife.
This new synthetic ATF fluid can withstand higher temperatures than the conventional oil.
In fact, according to a posted email exchange on Toyota-4Runner.org, we learned the fluid can operate as high as 280 degrees albeit for a short period of time before it decreases quickly. It is worth noting this decreasing quality is much slower than conventional fluid according to Valvoline.
Finally, Valvoline also says if your transmission runs hotter than 200 degrees, they recommend having it checked out. In their view, a transmission shouldn’t be running that hot.
Driving around empty is one thing, but what happens to the transmission when you are towing a heavy load? Our understanding is towing a truck can add around 35 degrees of increased temperature for the transmission. This means, if the truck is already running at 220 degrees, it should top out at less than 260 degrees.
While 260 degrees seems like it is quite high for a lot of owners, Toyota says this is within the acceptable range for the truck.
The question really isn’t about the fluid as even Valvoline says their fluid can withstand the higher temps, the question is about the transmission parts — clutch, seals, etc. Can those parts withstand the heat? Toyota says it can.
Why change it at all?
The biggest question (and frustration) for many owners is why even make the change at all? With one of the most highly thought of powertrains for reliability, this change seems backwards.
Toyota’s Chief Engineer Mike Sweers told us in an interview, Toyota made the change after discovering they no longer needed the part to keep the transmission within acceptable operating range.
Basically, engineering was out testing the truck, as all automakers do, and discovered they simply didn’t need the cooler to hit their operating range targets. By removing the transmission oil cooler, they could still be within an acceptable range and, according to Toyota, they would not damage the transmission.
Our video interview with Sweers includes his answer:
The transmission does still have a heater to warm up the fluid on cold days as well as an engine oil coolant to reduce heating issues.
It is worth noting, we reached out to our YouTube viewers for their truck’s automatic transmission fluid temperatures. Unlike Toyota, many automakers have an electronic gauge available to owners on the dash. We have received many different responses with different brands of trucks, engines from across the country. It seems, to us anyway, the newer trucks are running higher temperatures than the older trucks. This is pretty odd considering all other half-ton trucks come with a transmission oil cooler when selecting the tow package.
Finally, we hope Toyota will update their sales stickers after this story comes out. It sounds like a simple miscommunication between engineering and marketing.
What about other trucks?
Another question was raised by viewers about other truck makers. One in particular wondered: Why Toyota would eliminate something that is part of every towing package offered by other manufacturers? Naturally, this got our curiosity up on which other trucks offered a transmission oil cooler and if it was part of a towing package.
Turns out all the other truck makers offer one as standard equipment.
Specifically, Ram’s Trevor Dorchies, product communications and media relations for Ram Truck, said you don’t need any sort of towing package, it is standard equipment much the same as Chevy’s Mike Ofiara told us.
Ford said their new 2021 Ford F-150 “2.7L, 3.3L, 5.0L, 3.5L FHEV, and 3.5L all use the same trans mounted one cooler across the board. 3.0L has a unique trans cooler design that is common with the last gen 3.0L,” according to Dawn McKenzie, Ford Truck communications manager.
Nissan’s Steve Parrett, regional communications manager, said it is standard equipment on the Titan.
The bottom line on transmission oil coolers
For years, an auxiliary transmission cooler was thought to be a common-sense, standard piece of equipment on trucks designed to tow. Now, it seems like there is some disagreement between Toyota and consumers on whether or not you need it.
The real controversy is really about how long the transmission will hold up to the additional heat. Newer synthetic fluids don’t seem to be the issue — the parts are the real concern.
Toyota running their trucks without coolers sounds like a bad idea, yet we haven’t heard of a rash of transmission problems related to overheating.
In our view, the owner, mentioned above, either has a sensor issue the dealer can’t locate or something else is amiss. And we agree, it definitely seems like Toyota owners have been misled thanks to the sticker.
What do you think? Is this a big issue or a small issue many people are making into a big issue? Are auxiliary transmission oil coolers a thing of the past?