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Discussion Starter #1
I've had a 2014 Sequoia for about 5 years and have pulled my current trailer for about 3 with no problems. I headed off for about a 2 and half hour trip. We'd gotten 30 minutes down the road when I noticed the transmission temperature gauge. was practically to the red line. I looked for a spot to pull over and by the time I could do so the needle was pegged and the light was on. We let it cool down for a bit, then resumed. It gradually began to climb again. I tried taking it out of Tow/Haul but whether that was on or off made no difference. Thirty minutes later we had to stop again. After about 5 minutes the needle was in the middle normal range and we took off again. This time I slowed down from 65 to 60 and while the needle climbed way above normal,say about 85-90%, it didn't hit the red line again. This is the first time this has happened. The next day I took it out on the highway without the trailer and everything showed perfectly normal.

I'm at a loss where to start. I don't know if I'm really running that hot or if the gauge is faulty. I'm not sure if I need to go to a Toyota dealer, a transmission shop, or a local mechanic. Any thoughts?
 

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What's the mileage on your rig and when was the last time you changed the fluid in the transmission? My first action would be to change the fluid and see how the transmission responds.
 

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Mileage is about 94K. When I got the vehicle used I went over the maintenance manual and created a spreadsheet that I use to manage it. Changing fluid or filter was not a recommended or required maintenance item. That surprised me, so I double checked and the unit is sealed, so i presume that's the reason.
 

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As you say the transmission is sealed which pretty much means you do not need to check the fluid levels and there is no mandatory maintenance. It doesn't mean you cannot touch it though, since you have the overheating issues I would definitely replace the fluid to start with. Internet says you can do it yourself by measuring the quantities of fluid out and in precisely or you could let Toyota do it for you, from what I heard is it approx $200 to make it.

To further assure you that it is doable, my 2014 had it done by the previous owner at 105k miles. I know she didn't tow anything over 1000 lbs and still was kind enough to do it as a preventive measure (I really love the fact she did all the service at the dealership and therefore it shows at Toyota owners website). Since your fluid already got once (or more) to high temperatures it will be a bit burned through just like oil gets and it will be even easier to get it to overheat again.

154636
 

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As you say the transmission is sealed which pretty much means you do not need to check the fluid levels and there is no mandatory maintenance. It doesn't mean you cannot touch it though, since you have the overheating issues I would definitely replace the fluid to start with. Internet says you can do it yourself by measuring the quantities of fluid out and in precisely or you could let Toyota do it for you, from what I heard is it approx $200 to make it.
I think for the price it probably is a good piece of preventative maintenance, and I'll plan to do it.

That still leaves the following question. The transmission temperature on the gauge reads perfectly normal when not towing. And it's read perfectly normal when towing until last week. Given the towing package is supposed to have a transmission oil cooler, it's hard to see how that could not keep it cool if it were functioning properly, or at least why it would show differently towing or not towing. I did read that Toyotas and Tundras were having the same problem a few years earlier (where temperature would be fine for several years, then begin to heat up when towing) but no post I read indicated that anyone ever found the problem.

Put another way, I will change the fluid and filter to prevent future problems. But, logically, I'm not really expecting that to solve this immediate problem, unless I'm missing something (which is certainly not impossible).
 

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I'm no mechanical engineer but this is how I see it:

Towing puts load on the gears (with heavy trailer probably doubles it), load = energy, energy=heat. You said yourself, towing package includes transmission cooler. If towing didn't cause the transmission to heat more they wouldn't include the cooler in the towing package.

With age and mileage the oil looses it's lubrication capabilities. That's why we change the oil in the engine, transmission fluid is just different oil. When the gears are less lubricated they put more resistance -> generate more heat. Any minor debris like shavings in the gearbox will cause the same.

By my limited logic: if you change the fluid you will gain better lubrication, potentially get rid of any debris plus fresh fluid may have better heat absorption capabilities and flow better through the cooler and therefore improve transmission heat exchange. If it's a close balance minor changes may tip the scale completely and result in difference between your gearbox running warm or overheat.

Check this video:
 

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Discussion Starter #7
Watched the video. If I recall right it was a 2019 after Toyota had ceased providing a cooler, but supposedly had better oil and trannys. So not sure how relevant it is to a 2014. Still, I do plan to change the fluid and filter.

When I drove the Sequoia back, same behavior only I observed it more closely. Transmission temperature did not seem connected to outside air temperature, or to going uphill or downhill. It may have been connected to RPM but couldn't tell since tach responds immediately and the temp gauge more slowly. But it didn't necessarily seem connected.

Over the 2.5 hours it redlined twice or three times. But it would stay in the center a great deal, then slowly climb for reasons that were not obvious, but often at about 85-90% it would level out and then start back down.
 

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My intend with the video wasn't about the cooler (despite video's title) but about how transmission temp is related to load, climbing and descending from the passes plus what is the range of the temperatures to expect.
 

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My intend with the video wasn't about the cooler (despite video's title) but about how transmission temp is related to load, climbing and descending from the passes plus what is the range of the temperatures to expect.
OK. Thanks. Given it overheats on the small hills around here I'd be in a world of hurt to make a trip to real mountains as we've been contemplating. Guess I'll try to get the fluid/filter changed soon and see what that might do.
 

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OK. Thanks. Given it overheats on the small hills around here I'd be in a world of hurt to make a trip to real mountains as we've been contemplating. Guess I'll try to get the fluid/filter changed soon and see what that might do.
I did a study on 2nd Gen Sequoia transmission overheating several years ago. I wrote up the results here: overheating documented While my problem may not be directly related to yours, you might find the writeup to be informative.

It is important to understand that the "temperature gauge" is not really a gauge. It is more like an idiot light. The needle does not move over a wide range of temperatures which Toyota considers "normal." When the needle moves up past the normal position in the center of the gauge, you are already well into the "danger zone" (240 - 250F) where the transmission pan temperature is way above the normal value of around 200F.

The advise to change the fluid after overheating is good. When towing, try to keep the torque converter locked by gearing down and keeping the revs up.
 

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I did a study on 2nd Gen Sequoia transmission overheating several years ago. I wrote up the results here: overheating documented While my problem may not be directly related to yours, you might find the writeup to be informative.

It is important to understand that the "temperature gauge" is not really a gauge. It is more like an idiot light. The needle does not move over a wide range of temperatures which Toyota considers "normal." When the needle moves up past the normal position in the center of the gauge, you are already well into the "danger zone" (240 - 250F) where the transmission pan temperature is way above the normal value of around 200F.

The advise to change the fluid after overheating is good. When towing, try to keep the torque converter locked by gearing down and keeping the revs up.
Thanks. I'll read that shortly. It probably will be informative as I'm not a mechanic.

What you said about the temperature gauge being more like an idiot light I had not heard. Toyota's doing that sounds both bizarre and dishonest to me. One expects a gauge to be a gauge.

As to the part about gearing down and keeping the revs up, I thought that was what Tow/Haul Mode did. What exactly does tow/haul mode on a 2014 Sequoia do?
 
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