2025 4Runner Transmission Overheating on Climbs Off-Road

[NotApplicable]

I look for this issue every time I’m off-road - constant scan of T’s & P’s just like any aircraft I’ve flown. I just haven’t had any issue at all. I do use a standard setup off-road (except Green easy stuff), 4Lo, S1-S3, SDM, MTS - Rear Locker or Crawl/Decent as required but that’s infrequent. I understand the frustration folks are having with this - it’s kinda’ like the brake squeal, just shouldn’t have to worry about it after the investment we made in the vehicle. I’ve used this setup over and over in high altitude, low altitude, cool temps, over 100 F ambient temps for hours, prolonged climbs/descents - no transmission overheat issues.

Makes sense, sounds like you aren’t using 4Hi which, based on reports, is required to cause the issue

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[a_double]

Having to use 4Lo on a paved moderate incline where there’s no chance for tire slippage is contrary to the owners manual.

 

[3rdRunner]

Having to use 4Lo on a paved moderate incline where there’s no chance for tire slippage is contrary to the owners manual.

Never use 4Lo on pavement, only off-road. If I was concerned about Transmission Temp I would use manual (S) or Tow/Haul - keep the engine revs higher. Understand and agree that this is certainly something we shouldn’t have to be worried about.

 

[ropdykex11]

Updating my thoughts on this:

Did a full weekend of REAL offroading, under multiple conditions. Fully loaded cargo, rooftop tent, racks, bumper, winch, everything.

Fast washboard roads, slow rutted crawling, rock crawling, steep articulated climbing.

4hi most of the time, 4lo when crawling.

I saw transmission temp spike SLIGHTLY from halfway to 3/4 max? (from a 5 to a 7, gage has no numbers), but otherwise no issues.

60deg ambient temp, not high elevation. I think if it was WAY warmer and higher elevation, it might have become an issue.

My current thoughts: not a major problem for my use case. I'd be interested in a transmission cooler upgrade if one becomes available, but otherwise NBD.

 

[Iconic Fabrication Offroad]

Updating my thoughts on this:

Its available! Let me know if you have any questions. Iconic Fabrication is a new paying vendor on this forum. 3/4 of the way up the gauge could be concerning. I don't have data on my personal 4runner of going that high but the gauge is not "accurate" so to speak. Dead center on the gauge tested anywhere between 140 to 200 degrees F on my 2026.

https://iconicfabricationoffroad.com/products/2025-4runner-transmission-cooler-kit

 

[RunnerRocks]

Between 140 to 200 degrees F and the gauge stayed dead center without moving ?

 

[Iconic Fabrication Offroad]

Between 140 to 200 degrees F and the gauge stayed dead center without moving ?

Yes! I tested this with my Veepeak OBD Scanner and several apps including Torque Pro and Car Scanner ELM apps.

 

[big_ol_Jabroni]

The other day I was doing an offroad climb. It was the road to Cerro Gordo Ghost Town, if anyone is familiar. The first section I climbed 2.5k feet in 5.0 miles. It was around 95 Degrees F that day at the bottom of the trail. The average grade was 10%. I kept it in 2HI S2, or S3 if I went faster than 20 MPH. About halfway through the first section, I had to start going a bit slower and eventually transmission temperature started to climb. It got to the temperature shown in the image below.

I shifted it into 4Lo and kept going to finish the first section, but the temperature never went down. It just stayed at the position in the photo. Usually when I switch into 4Lo the temp will go back to center. After I finished the first section I put it in park and let it cool for about 5 mins and the transmission temp went back to center. The next section of the trail was 17% grade and only a mile. I was crawling between 0-10MPH in 4Lo and then the gauge shot right back up to the temperature shown in the original image. I then let it rest for 5 mins again to return to center and went on my way to the third section of the trail which was 14% grade for 1.2 miles.

I completed the trail without any over heat warning, however I am genuinely wondering if it is normal for the temperature gauge to budge in 4Lo. Note that when I was in 4Lo, I did not use S Mode, just D mode.

I am considering replacing the stock tires with heavier KO3's, in 265/70/R18 in D Load Rating. 54 pounds a piece vs the 38 Pound OEM Falken Wildpeak tires. I have accepted that for this truck, anytime you wheel you should be in 4Lo. I want the additional protection of these heavier tires since I usually wheel solo, however I am deeply concerned this could potentially lead to my truck being unusable / overheating in 4Lo.

Curious to hear if you guys think I am critically overthinking or share similar concerns.

 

[3rdRunner]

The other day I was doing an offroad climb. It was the road to Cerro Gordo Ghost Town, if anyone is familiar. The first section I climbed 2.5k feet in 5.0 miles. It was around 95 Degrees F that day at the bottom of the trail. The average grade was 10%. I kept it in 2HI S2, or S3 if I went faster than 20 MPH. About halfway through the first section, I had to start going a bit slower and eventually transmission temperature started to climb. It got to the temperature shown in the image below.
View attachment 44767

I shifted it into 4Lo and kept going to finish the first section, but the temperature never went down. It just stayed at the position in the photo. Usually when I switch into 4Lo the temp will go back to center. After I finished the first section I put it in park and let it cool for about 5 mins and the transmission temp went back to center. The next section of the trail was 17% grade and only a mile. I was crawling between 0-10MPH in 4Lo and then the gauge shot right back up to the temperature shown in the original image. I then let it rest for 5 mins again to return to center and went on my way to the third section of the trail which was 14% grade for 1.2 miles.

I completed the trail without any over heat warning, however I am genuinely wondering if it is normal for the temperature gauge to budge in 4Lo. Note that when I was in 4Lo, I did not use S Mode, just D mode.

I am considering replacing the stock tires with heavier KO3's, in 265/70/R18 in D Load Rating. 54 pounds a piece vs the 38 Pound OEM Falken Wildpeak tires. I have accepted that for this truck, anytime you wheel you should be in 4Lo. I want the additional protection of these heavier tires since I usually wheel solo, however I am deeply concerned this could potentially lead to my truck being unusable / overheating in 4Lo.

Curious to hear if you guys think I am critically overthinking or share similar concerns.

I may be missing something here because I don’t see where you had an issue…and I’m not trying to be a smart ass or critic. Based on the conditions of the climb you described , I see a small rise in transmission temp. I would expect that and not be concerned unless it continued to progress toward the marked high range. I know there is a lot of talk about transmission overheating issues so folks are concerned. I personally don’t perceive this as a problem, more of an expected response to the conditions. What am I missing?

 

[big_ol_Jabroni]

I may be missing something here because I don’t see where you had an issue…and I’m not trying to be a smart ass or critic. Based on the conditions of the climb you described , I see a small rise in transmission temp. I would expect that and not be concerned unless it continued to progress toward the marked high range. I know there is a lot of talk about transmission overheating issues so folks are concerned. I personally don’t perceive this as a problem, more of an expected response to the conditions. What am I missing?

My concern is based on the fact it took a mile on a 17% grade in 4Lo to increase the transmission temp from the centerline to the the point on the image. I never found out if the temp would stabilize or would keep climbing because I decided to pull over and let it cool. Since this is my first 4X4 I wasn't really sure if this was expected behavior based on the conditions I described.

I am about to upgrade to heavier tires (but still stock diameter) but with all the issues I read about offroad, I am worried I could be significantly accelerating the rate at which my transmission heats up.

 

[3rdRunner]

My concern is based on the fact it took a mile on a 17% grade in 4Lo to increase the transmission temp from the centerline to the the point on the image. I never found out if the temp would stabilize or would keep climbing because I decided to pull over and let it cool. Since this is my first 4X4 I wasn't really sure if this was expected behavior based on the conditions I described.

I am about to upgrade to heavier tires (but still stock diameter) but with all the issues I read about offroad, I am worried I could be significantly accelerating the rate at which my transmission heats up.

Right..understand you were being cautious and I think that was smart especially in light of the comments on here about overheats during climbs. I’m running the 35/11.5/17 Toyo RT Pro which weighs 66 lbs. Haven’t had any issues with transmission temp and have had the vehicle in prolonged climbs ( Engineer Pass ) and very hot, difficult terrain Palo Duro Canyon. I do use 4Lo, S1-3 for the majority of my off road use, though I did 120 miles of beach/loose sand in 4H yesterday in high 90’s temps with no overheat issues. I think you’re going to be ok with a larger tire but some of the folks on here who have had issues may be able to provide some more insight.

 

[127.0.0.1]

don't worry about the temp gauge until it hits red

from center to the hot side, and not red, is fine

if you are going close to red but not over, a lot, or often....
the do severe service intervals on tranny have have the
3-ish quart drain and refills done to keep it fresher

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