High transmission temp warning

I was recently offroading and had a full truck with rooftop tent...we were going up quite an extended incline at slow speed (I was in 4 wheel hi) and I got a warning for high transmission temp. Stopped the truck and let it cool...warning went off and finished the hill and the rest of the trip with no warning...

So is it time for a transmission cooing system? I do love offroading and tend to have all my overloading gear...don't want to run into this issue in the future!

 

Also looking for an updated gauge system that will help me monitor transmission temp, etc.

 

I’ve got the Scan Gauge III and really like it. Can monitor a lot of items all at once.

 

I use the OBD fusion app and an OBD reader purchased off Amazon. Gives the pan and converter temp readings.
Also have a cooler but maybe you should have been in 4 low especially with bigger tires/lots of weight, or at least in tow/haul mode and s mode locked in a lower gear, or all the above.

I drive my truck in tow/haul s-mode 24/7, it makes a difference on the driveability and the trans abuse/temp

Definitely service the trans as @ColoradoTJ mentioned.

Nice setup by the way!

 

No cooler needed. Toyota says "ok" good to go, no cooler needed. Let warranty / Toyota cover if an failures occur.

 

Are you able to get engine oil temp with the III?

 

If a failure occurs it more likely than not going to be outside of the warranty period. As others have said, when off road use 4lo, 4hi is more for on road use like snow, unless you're flying through dunes or something over the speeds for 4lo. I installed the kit from @Genuine Cooling Systems and no longer worry about trans temps although I do still monitor just because I like to, now I stay at a nice 185° - 195° unless going up inclines then it will rise but immediately drop back down quickly afterwards.

 

Slow speed in 4hi will overheat your transmission. If you are going under 20 MPH and need 4WD run it in 4Lo.

 

I can’t remember, I will check today and up this thread.

*Update does not appear Toyota offers an engine oil temp to display.

 

I'm not sure if a cooler would have saved the OP in this instance. I think the bigger issue was using 4HI at low speeds.

If you're not moving very fast, I am not sure that there would be enough air being pushed through the cooler to make a huge difference. I installed a cooler on mine, but the purpose was to help transmission temps when pulling my trailer down the freeway, not for off-roading or 4WD use.

 

What does the owners manual say?

 

From my 2021 Manual:


“4H” (high speed position, four-wheel drive)
Use this for driving only on tracks that permit the tires slide, like off-road,
icy or snow-covered roads. This position provides greater traction than
two-wheel drive.
The “4HI” indicator will come on.
“4L” (low speed position, four-wheel drive)
Use this for maximum power and traction. Use “4L” for climbing or
descending steep hills, off-road driving, and hard pulling in sand, mud or
deep snow.

Based on this, I would use 4L at low speeds.

 

I would swap the trans fluid or at least do a drain and fill. And get a trans cooler and monitor trans temps.

The light coming on means it got REALLY hot. My trans got hot once, and the light didn't even come on and the trans was fried. Though this was a unit with 200k+ on the clock, so I would be proactive now and replace the fluid every couple oil changes.

 

Another vote from me for the OBD fusion app, its great and its pretty cheap. Like others have said, your main issue was likely the 4Hi. I do mountain offroading and use OBD fusion app and even with the tranny cooler that I put in, it will get hot pretty fast in 4Hi at low speed as there isnt much air flow getting to the tranny cooler. I started using 4lo more after seeing that. I felt like 4lo wasnt needed and it was just working the truck too hard but its actually the opposite. It just uses more gas. Also, I have found that locking the truck in 2nd or 3rd also helps keeps the temps down rather than just offroading in D.

 

Fair point.

 

Thanks for all the input! I am going with the ScanGauge 3...like the little monitor...
also going to get my transmission serviced and get the cooler added...just a piece of mind thing!

 

Don’t forget you also need to regear your truck for the larger tires.

 

I dont know how much that would actually help since the radiator fan is behind the radiator and the trans cooler is installed in front, so your only getting what ever hot air from the radiator gets in front. You could however install a fan onto the trans radiator itself which would definitely help with slow moving off roading.

 

Learned something new today.

 

I’m glad I stumbled upon this. So I had the same warning come up yesterday on my pro. The only difference was that i was in the regular drive mode (2WD) since the trail i was on was nothing crazy. Definitely not one that required to be in 4Lo. The trail consisted of a moderate steep grade for about a mile and a half. Driving never went over 15mph with most of it hovering around 5-7mph’s. Temp outside was at 70 degrees. I’m running 37’s on stock gears and had 3 passengers in the truck along with my baby. I’ve done this trail before with my 19 Tacoma and never had an issue. Trans light came on about 3/4th’s into the trail and I seriously thought it was a joke.

the only thing i can think of is bringing it up to the dealership but they’re going to tell me to kick rocks since I’m running 37’s.

anyone run into this issue off-roading in the regular drive mode?

 

Going 5-7mph uphill for a mile and a half in a big heavy truck with tall tires is going to generate a ton of heat in the trans. It's not about the speed, it's about the load on the engine and how much the trans and converter are slipping. 4lo isn't just for rock crawling in these trucks, it takes a ton of stress off the engine and trans and from what I've seen can drop trans temps by 40+ degrees on hills.

 

I understand. I figured the trail wasn’t very difficult or lengthy so I thought I could get away with 2WD with no issues. Ive never had any issues with my other trucks with high temp warnings on easy trails but then again they’ve all been mid size rigs on 35’s.

My truck has 3777 miles on the odometer. I feel like after getting that warning it’s a must I service the transmission.

You think I can get away with driving it for another 1300 miles before taking in?

 

I’ll take it in. Rather be safe than sorry.

unfortunately gears aren’t out yet for the gen 3’s. That was one of the first things on my to do list after going up to 37’s.

I heard a company was working on them, but can’t remover who.

 

I used to think the same until I started monitoring my trans temps. It was pretty alarming how hot it got, and how fast it got there.

That's where an obd2 app or something like an ultragauge comes in handy. You can try the hill (or whatever) in 2wd or 4hi and if it starts to get hot, just switch to 4lo. No guessing, and you'll know what's happening long before it gets hot enough to hurt anything.

 

good to know, you live and you learn. Definitely ordering a Scan Gauge after having gone through this. Thanks for the info!