Transmission running hot, part 2 and update - final verdict

Most of you probably saw my previous thread complaining about an overheating transmission condition during unloaded 4x4 operation on mild hill climbs. After extensive dealer testing all was deemed normal and transmission operating as designed.

Short version update: Truck still does it and overall just sucks for 4x4 use. And, in my experience is probably questionable for any kind of real load use.

Longer version: I removed skidpates to rule out that as a possibility for lack of air flow causing the issue. Definitely not the problem. I knew I was in trouble when, on the way to the ranch on the highway, I hit some slow construction traffic going up a pass. Tranny got hot. 7/8 way up the gauge. Completely unloaded, and in the high 60's ambient weather temp. First time I've personally seen this in 2wd on-road conditions (although the dealer was able to get it hot doing this). I shudder at the thought of what would've happened had I been towing my 5000# trailer, as there was no place to pull over. Lame.

Got to the ranch and did lots of experimenting. In 4H, it got hot again, as expected. In 2wd, it did too, though, on average, not as hot and not for a more prolonged period. Tow Haul setting helped even more. But, it would still get hot if you let it. Surely would have redlined, had I let it.

Switched into 4L and the situation was greatly improved, but it would definitely still get warm, maybe 3/4 on the gauge, but no redlining. BUT, and this is a huge one... drive conditions in 4L are miserable, as is typical, especially when it shouldn't even be needed because the hill isn't even steep. Not pleasant for any extended use at all. AND... The truck is a giant PITA to get to go into 4L most times. You have to back up and then forward, tinkering with the switch multiple times before it will engage. SOOOOO frustrating. Especially when switching in and out frequently to keep it from overheating. I miss a manual lever.

So my unfortunate conclusion (and surely going to be an unpopular opinion here) is: This truck is a turd. At least for my use. It's just not a durable and tough 4x4, as was evident from the get go with the simple omission of recovery points. To me, it's an $80K disappointment. Worse yet, even if I sold it and moved on, I'm not sure any other 1/2ton truck option is any better, all things considered. So I think I'll continue to deal with the truck until maybe the mid-cycle refresh and hopefully Toyota pulls their heads from rectums and augments the trans cooling. Or I'll at least wait until my warranty expires and I'll install an aftermarket tranny cooler.

It's just sad. I won't bore you with my other minor QC issues I've got, but it's quite clear to me there is an obvious departure from the previous generations of Toyota products where the focus was clearly on building reliable and durable trucks, albeit at the expense of outdated tech and lousy fuel economy. That focus seems to have reversed. Seems now, the business model is focusing less on robust quality and more on economy and silly tech/bells and whistles and chimes. Soccer moms and dads must be the new target market. I miss the old Toyota. Done ranting.

 

Thankyou for the update. I would not be happy either.

 

Sorry for your problems, not cool for such an expensive truck. I know you said the dealer tested it and deemed it normal, but did they tell you they got the same temp. readings you're getting? I can understand it getting hot in 4/HI at low speeds like you described in your earlier post, but it overheating in 2WD unloaded sounds like you may have a problem not diagnosed yet.

 

Well, the dealer actually said they were able to get it hot in 2wd on the road too. I watched the trips they made on the app and it was a 2-3 mile hill climb they did over and over again, going slow, unloaded. They had it hooked up to the computer and video'd it all, communicating with Toyota engineers. Gauge almost redlined. Normal, given the conditions (laughable!), is what they said. They even replicated the exact same conditions with two other Tundras they took off the lot. The service techs involved were blown away.

 

I would question your gauge accuracy. I tow 5-6000 pound trailers uphill all the time and the temp gauge never moves.

 

Soo, no real performance issue, you just don’t like the gauge reading high?

 

Gauge accuracy was checked and verified normal too. Try pulling that load up a hill at slow speed.

And to be clear, the trans temp gauge is what I’m talking about. You are correct the engine coolant temp never moves.

 

Partially correct. No performance issue, but also because I would stop the vehicle and let it cool before it got to that point. I’m sure if I kept the tow gauges off and/or disregarded the trans temp and kept driving as I have always previously done without issue in previous vehicles, I would have had all sorts of check engine and warning lights go on.

 

Not a Tundra, but TFL went up a mountain pass in Colorado with the new Tacoma on a dirt road and the transmission was getting real hot to the point they thought they would have to stop to cool it down. I haven't towed anything remotely heavy with my Tundra yet, but my transmission stayed relatively cool driving in town with my ATV trailer attached. I'm curious now how it will be when I tow the travel trailer this summer.

 

I guess we will never know. Does blackstone or whatever check trans fluid? You should suck some out and send it in, might be interesting.

 

Where exactly do you monitor the just the transmission temperature itself, I only have oil and coolant temp on my dash.

 

Are these worries based only on a trans gauge built into the dash that doesn't contain any actual numbers? I would hesitate to get very concerned about that. Toyota (at least lately?) appears to be using gauges that actually move instead of the dummy gauges. I'll link to two videos below: the first is me towing my toy hauler (~5,500 - 6k lbs loaded) over a mountain pass in WV. I use a scangauge III and display my trans temps which never got too hot. The 2nd is of a mechanic from Canada that speaks to his surprise when finding out the Tundra actually uses an oil pressure gauge that moves with the pressure instead of a "Good / Not Good" dummy gauge. I'm not saying you're wrong. I'm not saying your truck's trans isn't running too hot. I'm just wondering if possibly you're used to looking at trans temp gauges that don't move? I don't know. I'm perfectly happy being completely wrong about this. Just pointing out some info/data for consideration and I'm curious what your actual numbers are.

Towing with SCIII: Does the New Tundra Need an Aux Trans Cooler? - YouTube

Mechanic's comments on the Oil Pressure Gauge: Toyota Tundra 3.4L Twin Turbo I-Force Engine | How Does It DRIVE?? (youtube.com)

 

Counter perspective: Every vehicle you’ve used before and thought was totally fine in 4Hi was undoubtedly running too hot, too.

I posted in your Part 1 thread that I got my 5th gen 4Runner transmission too hot. Mild towing and off-roading in 4Hi. Torque converter started slipping @ around 131k miles. Never got a warning because I didn’t get it hot enough to trigger the warning light. But it was hot enough to do damage over time.

Same is true of all your other vehicles you like to crawl steep grades with in 4Hi. Your Tundra is just the 1st to warn you about it.

 

Toyota certainly has been moving towards pleasing share holders over customers for some time now. However, they still produce the most durable vehicles.

If you plan to keep the truck well past warranty, add a cooler now.

You may want to look and see if the thermostat on the transmission can be pinned open.

Drain and fill pan to inspect atf.

 

The trans gauge is not a dummy gauge. It moves digitally, very obviously, and incrementally as it gets hot. I would assume that touching the red means very hot, as is logical. Also as logic would dictate, I did not push it beyond that point. Even the dealer verified it was getting hot, surprisingly so, to the point where even the service techs were blown away. They thought for sure there was a problem with my truck until they got Toyota Engineering involved and they said it’s working as designed. And then they verified it with two other Tundras.

As for other trucks doing it too and not showing it, not exactly true. My diesels, Ford and Dodge, had auxiliary aftermarket gauges, they never got exceedingly hot, never over 200. My buddy at the ranch followed me up the same road in 4H in his new Dodge Rebel. While I stopped to cool down I checked with him, 192 degrees in his trans temp that reads real numbers. I’ve also driven my buds newer F150. No issues. And in my experience, you can feel, and smell when a trans overheats. Even in my previous 4Runners with dummy gauges, I never experienced anything remotely close to worrisome on these same trails and conditions.

I’m not alone in this. Others have reported similar complaints under similar conditions. It’s just the way the truck was designed. The engineers obviously never thought of slow speed use with lack of air flow.

 

Go through your settings to change the right side gauges to tow gauges.

 

Why not pickup a Scangauge II or III and see the actual numbers? I'm not being a smart-ars, just legit wondering. I'd be way to curious to know the actual numbers (Toyota's red zone could be Ford/GM's normal zone?). Either way, sorry to hear it's doing this to you. I've towed 7k lbs through the mtns of WV in the middle of summer and never hit concerning temps (monitored it with a SCIII). Hopefully it's an isolated issue that can be resolved.

 

Do they have PIDs for the transmission for 22+?

 

I may pick up something like that, I’m just not thrilled with the idea of throwing more money at an expensive truck Ive already fallen out of love with. I have other issues too. The wind noise and the blurry windshield drives me nuts. I may need to move on for sanity’s sake.

What’s the difference between the Scangauge 2 and 3?

Next time you’re towing through the mountains, slow down to 10-20 mph max and monitor what happens. The trans hunts for gears like mad, generating gobs of heat.

 

Don't wait till it disintegrates, install a cooler.

 

So that when it does blow under warranty, Toyota can claim the aftermarket installation contributed to the problem? I’ve been down that road before.

 

When it blows naturally 1 day out of warranty, it's you who will pay for it. Insufficient cooling you can fight for in the court. Toyota has to prove its design is sufficient. Just keep a few videos ready.

Last 3 if not 4 years of Gen2.5 had been running without cooler as well. Mine was reaching over 250 F just going freeway at 50 MPH in 50 degrees weather. I don't give a sh.t about the warranty, I installed a cooler. I knew if I wouldn't, it will be due for rebuild very soon.

 

Same with gen2.5. Sometimes was taking me rolling back and forth a minute or two in winter. Then I replaced the transfer case oil with Ravenol MTF-3 and now it's always 1-2-3-done.

 

I'm almost convinced to get a Scangauge and report back with a part 3 update where I will equate the real temperatures via Scangauge to the level on the Tundra dash gauge. If for no other reason than to satisfy curiosity.

 

Not 100% related but I have towed my 5500 lb travel trailer about 2400 miles now with my new to me 2018 LX570 with the 8 speed transmission and found that the transmission stays cool 99% of the time until the truck goes into 4th gear or lower climbing a grade. The reason for this is that the torque converter unlocks below 5th gear, but is always locked 5th gear and up.

The LX comes with a radiator end tank cooler and a decent sized air cooler in series for the transmission, but even with that air cooler it still will get up to the 240-250's pulling grades in 3rd or 4th gear even when its only 50* outside. If it stays in 5th gear or higher, its zero issue and wont exceed 200F in any circumstance I have witnessed.

Previously I pulled the same trailer with my 2014 F150 over 22000 miles. That thing NEVER got hot but it also never unlocked the torque converter at any reasonable speed in T/H mode.

the other issue is that I think at low speeds you are getting very little coolant flow through the radiator. since the tundra only has the liquid to oil cooler then the limited flow rates are probably hurting the situation and with no air cooler to provide a secondary way to expel heat at low speeds, the trans just goes hot.

I kinda wonder if running in T/H mode may help the situation. Most tunes I have looked at run a different torque converter lockup schedule in T/H mode and so it may keep the truck locked up more in those lower speed situations.

 

Mine is a 19, first year they deleted the transmission cooler. I encountered the same problem, on forest roads, no need for 4lo, and got a temp warning in 4hi. Bought a gauge to monitor temps via obd2. Found my tranny temps were running 240+ on the highways before even starting the trails and would quickly go up from there in 4hi to 270+. Bought a tranny cooler and temps usually never climb above 190 in normal conditions, Toyota keeps saying these trucks will operate fine at high yemps, 280+, I don't think 2.5s even give a temp warning till 305 or there abouts. I'll never feel comfortable at those temps, I monitor my transmission temps full time just for piece of mind, but I know nothing of the 3rd gens.

 

Are these pan or TC temps? My TC temps on climbing grades goes up into the 240s-250s occasionally, but my pan temps have never gotten over 230.

Edit: Towing my 8000# TT