Overheating Transmission

[usa4x4]

I do not own an LC yet but have experience with my 2007 FJ.
Last year my son and I were traversing the Washington state discovery route. I also had a transmission over heating issue. My problem was going up a hill in drive mode which on the FJ is overdrive mode. We were going slow,5-15mph.
Once it was cooled down, I found that running in 4th or Third solved the issue. Being that the new LC has an electric fan, could that be an issue?
Does it run at one speed all the time?
With conventional fan you can control the fan speed by changing gears.
Just a thought.
I apologize for crashing the post.

 

[Trail250]

I do not own an LC yet but have experience with my 2007 FJ.
Last year my son and I were traversing the Washington state discovery route. I also had a transmission over heating issue. My problem was going up a hill in drive mode which on the FJ is overdrive mode. We were going slow,5-15mph.
Once it was cooled down, I found that running in 4th or Third solved the issue. Being that the new LC has an electric fan, could that be an issue?
Does it run at one speed all the time?
With conventional fan you can control the fan speed by changing gears.
Just a thought.
I apologize for crashing the post.

I think its got something to do with ECU. Mine has been doing good so far this year so I am wondering if there was some OTA update that was released to let the transmission cooler work in 4H. Before transmission would get warm, but as soon as you switch to 4-low it drops fast. But I could also be full of it and not know what I'm talking about.

 

[ptahkeem]

Here is an explanation from ChatGPT. For reference, I made sure it confirmed its findings and had it cross reference itself.

In 4Hi, the vehicle still has high-range gearing. It has traction, but not much extra mechanical reduction. On a long, slow, steep climb, the wheels need high torque at low speed. If the transmission calibration chooses to stay in a taller gear or keeps the engine at low rpm, the drivetrain may use controlled slip across the converter/input coupling/clutch system to smooth power delivery and avoid lugging, harshness, or gear hunting. That slip turns mechanical energy directly into heat. In 4Lo, the transfer case adds mechanical reduction, so the drivetrain no longer has to create as much torque multiplication through slip. Less slip means far less heat.

That is the core phenomenon.

Toyota’s own material supports the calibration side of this. The LC250 i-FORCE MAX makes its peak 465 lb-ft at a very low 1,700 rpm, and Toyota says the 8-speed has uphill/downhill shift logic that helps it “maintain gear selection longer” during elevation changes instead of downshifting constantly. That is good for smoothness and road-trip feel, but it can be bad in a slow steep climb where the system is trying to pull hard at low rpm.

Toyota’s LC250 manual also makes the intended use distinction clear: high range is for normal/general driving, while low range is for steep climbs, mud, and situations requiring especially large driving force. That strongly supports the idea that Toyota expects L4L/4Lo to be used when the climb is slow, steep, and load-heavy.

The heat mechanism is real, not speculative. Toyota itself has published technical work on controlled torque-converter-clutch slip as a way to prevent engine torque fluctuation from being transmitted through the drivetrain while improving efficiency. Another Toyota-linked SAE paper notes that slip-controlled lockup requires ATF with anti-shudder properties and high torque capacity, because controlled slip is an intentional friction-control regime, not an accident.

Low rpm can make the situation worse because the vehicle may be lugging in too tall a ratio, the coupling/clutch may have to slip more, and oil pump/cooler flow may be lower. But the main heat source is not low rpm itself. The main heat source is sustained slip under high torque.

The transmission/hybrid-control calibration is biased toward low-rpm smoothness and efficiency, and in 4Hi that can allow too much controlled slip during long steep low-speed climbs. But the precise cause of overheating is:

high torque × sustained slip speed × insufficient time/cooling capacity = transmission/hybrid-module heat buildup.

4Lo fixes it because it replaces “slip-based torque multiplication” with gear-based torque multiplication. Gear reduction does not make significant heat the way a slipping clutch or converter does.

 

[ultane]

I apologize for crashing the post.

Welcome to the asylum.

No apologies needed. It’s an Internet forum, where exchange of information is welcomed.

 

[usa4x4]

For the three incidences you had, were you in 4H auto, 4H manual, or 4L? Reducing shifts by staying in manual shifting or 4L mitigates a rise in transmission temp at slow speeds.

Another thing is to always be out of the overdrive gears. I had the same issue in my FJ. You need the higher engine rpm to move the coolant through the radiator.

 

[ultane]

Well add me to the list….
…..Do better Toyota.

Aren’t we supposed to put it in 4 low to prevent that from happening, or when that happens?

 

[sweet5ltr]

Well add me to the list. I took mine mildly "offroad" this evening. Parsons Branch Rd in the Smokies (Cades Cove), which is a very easy trail/road. There were a couple sections where it was uphill but nothing crazy, some ruts, gravel but easily managed. I was in 4H and in Mud mode which really wasn't needed. I only put it to Mud due to some heavy rains and really just wanted to test it.
Anyway the transmission temp climbed dramatically almost touching red at one point. When things got easier it naturally declined, and maybe some of the little water crossings helped cool it as well. I am also in the camp where I don't us 4 Lo until necessary and this was totally not one of those times. I'm not a Toyota apologist and I just find this unacceptable for an "OffRoad" oriented vehicle especially one tied to the LandCruiser legacy. This trail can easily be traversed by an Outback or forester with no problem.

This is kind of a deal breaker for me and the only reason I haven't gotten rid of this LC already is because it still has temp tags, Its paid off, and I still haven't gotten my registration and tag preventing me from trading it in on something else. I was just starting to warm up to the idea of keeping it but this transmission issue is just sad, and I won't make excuses. Using 4Lo or manual shifting, etc is not the answer for such an easy trail. Do better Toyota.

View attachment 72054

Not sure how many times this needs to be said, but 4L / manually shifting will solve any and all of these overheating issues. This vehicle regardless of how people feel, is not designed to do really any off roading in 4H.

It's all cool though, if you want to smoke your transmission off road for not wanting to use 4L and leaving it in 4H/D, buy something else. I'm not sure why this is even a conversation, takes nearly zero effort.

 

[ptahkeem]

Well add me to the list. I took mine mildly "offroad" this evening. Parsons Branch Rd in the Smokies (Cades Cove), which is a very easy trail/road. There were a couple sections where it was uphill but nothing crazy, some ruts, gravel but easily managed. I was in 4H and in Mud mode which really wasn't needed. I only put it to Mud due to some heavy rains and really just wanted to test it.
Anyway the transmission temp climbed dramatically almost touching red at one point. When things got easier it naturally declined, and maybe some of the little water crossings helped cool it as well. I am also in the camp where I don't us 4 Lo until necessary and this was totally not one of those times. I'm not a Toyota apologist and I just find this unacceptable for an "OffRoad" oriented vehicle especially one tied to the LandCruiser legacy. This trail can easily be traversed by an Outback or forester with no problem.

This is kind of a deal breaker for me and the only reason I haven't gotten rid of this LC already is because it still has temp tags, Its paid off, and I still haven't gotten my registration and tag preventing me from trading it in on something else. I was just starting to warm up to the idea of keeping it but this transmission issue is just sad, and I won't make excuses. Using 4Lo or manual shifting, etc is not the answer for such an easy trail. Do better Toyota.

Hm… the fact that an Outback can drive the trail really has nothing to do with why your transmission temperature climbed. Very different weights and also a very speculative assumption. The LC is a 5,000+ lb truck and 4Hi doesnt give you gear reduction... You reported the trail has steep uphill sections. Were you crawling at low speed? I looked it up and the National Park Service describes Parsons Branch as an eight mile narrow gravel road with numerous stream crossings and steep grades. They also say that storms can make it difficult or impassable. I think its logical to reason that after heavy rains the ruts loose surfaces and uphill sections were conditions where the torque converter might have remained unlocked and that that generated a ton of heat. Mud mode might have also contributed to additional torque converter slippage as it typically encourages more wheel slip. I do think Toyota could have given the transmission more thermal headroom in 4Hi but saying 4Lo “isnt the answer” because the trail might be easy makes little to no sense. That sounds like a subjective opinion to me… Your temp gauge was showing that the transmission was generating heat under your driving conditions and your use of 4Hi but that doesnt necessarily mean that the transmission failed…

 

[ptahkeem]

Yes evidently but that is the dumbest thing I've ever heard and in all my years of dealing with off roading and countless off road vehicles I have never had to do this to keep a transmission from having hot flashes like a menopausal 50 year old female. I DON'T WANT TO BE IN 4LO, all the time when it is not needed. It is harder on the vehicle and limiting to the off road experience. Either Japan doesn't understand what it means to Off Road or they are compensating for a design error. Either way it is unacceptable and Toyota apologists just need to put their bias aside for a second.

Sounds like you might just have a bias towards not wanting to use 4Lo when necessary?

 

[sweet5ltr]

It's not designed to Off Road AT ALL evidently and I won't make excuses for a Company that is clearly is sharp decline in quality since the last 5 or 6 years.

I have driven 600 miles off-road, been to Moab a half dozen times. I'm not sure what kind of off roading you do, but my only limit has been how badly I want to bump and grind on the skid plates. I'm going back in October to do top of the world, you know, a very easy beginner trail .

But I'm also the type that uses 4L so maybe that's why I haven't experienced these issues

 

[ptahkeem]

It's not designed to Off Road AT ALL evidently and I won't make excuses for a Company that is clearly is sharp decline in quality since the last 5 or 6 years.

Trust me this trail is very easy and the uphill section was very short and didn't need 4WD at all to be honest. Face it this is a big miss on Toyota's part. The increase in temperature shot up way too fast for this to be acceptable. Manually shifting or using 4Lo is not the answer.

Curious why we have 4Lo… and the NPS is lying?

 

[sweet5ltr]

Curious why we have 4Lo… and the NPS is lying?

Guy who works with me nearly smoked the transmission because he refused to use 4L on a 3500 Chevrolet Duramax up a very steep, rocky grade, just this past week, overheated with multiple warning lights. I'm guessing there are a lot of people like this. Same people who will drive down the steep grade, riding the brakes in 4H rather than using 4L and manually shifting. Once that fluid is cooked it's game over on longevity.

 

[ptahkeem]

Guy who works with me nearly smoked the transmission because he refused to use 4L on a 3500 Chevrolet Duramax up a very steep, rocky grade, just this past week, overheated with multiple warning lights. I'm guessing there are a lot of people like this. Same people who will drive down the steep grade, riding the brakes in 4H rather than using 4L and manually shifting. Once that fluid is cooked it's game over on longevity.

I don’t quite understand… the tools are there… use them as intended? Also… what is crawl control???

 

[sweet5ltr]

I don’t quite understand… the tools are there… use them as intended? Also… what is crawl control???

Why does anyone need to air down, just continue to puncture tires and blame Goodyear or whomever. I see this all the time.

I don't get it. I was working at a telecommunications site in Montana, asked the guy how bad the trail was leading up to it and did we need to air down, of course he said no, it wasn't bad at all. Five minutes later I had a tire puncture as we drove over a mile on sharp, jagged rocks to the peak. Thankfully I'm actually prepared and carry repair kits and an air compressor in my work vehicle - otherwise I would have been changing a tire on the side of a mountain pass. Last time I listened to anyone in my field on off road advice.

The opposite is taking place here. Refusing to use 4L is just ridiculous.

I would say one of the greatest features of the LC is the tuning in 4L. It's absolutely phenomenal.

 

[ptahkeem]

Gotta love preparedness and due diligence =)

 

[sweet5ltr]

4 LO for what I experienced is overkill and honestly embarrassing if needed. Sorry it didn’t warrant 4LO. Well I mean obviously it does in theses land cruisers

Everything Toyota tuned into the LC is baked into 4L. Yes, they expect you to use it on basically any surface that isn't a paved road. I had no idea there was a badge of honor for not using 4L. Same badge of honor for not putting a part-time TF case into 4WD until being stuck i assume. Seen that many, many times. They lock the hubs after getting stuck and spending four hours waiting for a buddy to pull them out.

 

[ptahkeem]

4 LO for what I experienced is overkill and honestly embarrassing if needed. Sorry it didn’t warrant 4LO. Well I mean obviously it does in theses land cruisers

You’re not wrong! You drove uphill and in the mud. Page 437 in the manual:

H4 (high speed position)
Normal driving on all types of roads.

L4 (low speed position)
Driving requiring maximum power and traction such as climbing or descending steep hills, off-road driving, and hard pulling in sand or mud, etc. The low speed four-wheel drive indicator will come on.

Edit: corrected the page number.

 

[ultane]

I DON'T WANT TO BE IN 4LO, all the time when it is not needed.

Then use manual shift mode..

If you can’t do either of those (owners manual ‘suggestions’), the LC-250 is obviously not for you.

At least you can get a great price on you LC when you sell it.

 

[RideWithYanu]

4 LO for what I experienced is overkill and honestly embarrassing if needed. Sorry it didn’t warrant 4LO. Well I mean obviously it does in theses land cruisers

Sounds like your mind is set. Bye!

 

[ptahkeem]

4 LO for what I experienced is overkill and honestly embarrassing if needed. Sorry it didn’t warrant 4LO. Well I mean obviously it does in theses land cruisers

I guess you could solve this by purchasing an Outback?