2024 Transmission getting HOT in 4x4 climbing hills, skidplates?

We don’t really know anything until you have an actual temperature reading in degrees. The fact that you said the engine was “Really Loud” tells me the electronic clutch fan was engaged doing its thing. It is Loud when engaged at a higher rev. and when not this engine is pretty quiet with a stock exhaust. When you try this again with a scanner tool connected, get actual trans, engine coolant, and motor oil temps at the highest point.

 

A 21 isnt a third gen though. Do they have the same Transmission?

 

Is that an app or something?

 

For all those saying to use 4Lo, OK, OK. I hear you.

But I still haven't gotten a good mechanical explanation why it's necessary with this transmission and not in my previous vehicles. What makes this tranny design unique that requires 4Lo to keep it from overheating?

Is it just because they got rid of the cooler? Toyota has to be smarter than that, right?

 

Pretty much because the cooler is gone.

Toyota decided that modern transmission oils can take more heat before they break down, and that most of their customers use trucks like passenger cars. So they saved themselves production costs, padded their profits a bit, and deleted stand alone transmission coolers.

Pretty shitty.

 

But yet, at the same time tow ratings have also gone up considerably? How is that possible with a transmission that's less adequate? These things are supposed to tow 12,000#!

I haven't towed yet, but I do own a 5500lb camper and even at less than half the rating I'm nervous as hell thinking about towing it in the mountains.

 

You'll be fine!
https://m.youtube.com/watch?v=GZIx3wX5sJU

 

You have to understand that putting high load into the torque converter is heating up the transmission fluid. Toyota has two oil temp sensors, one in the pan and one right in the torque converter. The torque converter one is the first to get hot in high load. Like others said, 4L reduces the load on the torque converter due to the gear multiplication but also if you drive faster the torque converter goes into lock up and will reduce the heat build up significantly because the transmission fluid is no longer carrying the load. That said, I doubt a transmission cooler will help that much considering the localized temps in the torque converter when it’s slipping.

 

Also you’re looking for an explanation, but it’s a completely different design torque converter from other vehicles and it’s hard to say exactly what the cause is. Maybe the torque converter size, maybe other things. Did your 4Runner have an AT temp gauge?

 

That's a good explanation. Thanks. Do we know what the lock up speed is to the TC? That would be helpful info.

 

I have had 5 tundras (and a few Tacomas and 4runners). Some have had trans coolers, others haven't. My 21' TRD Pro didn't have any trans cooler at all and it was "fine" because they didn't include a gauge either. No Toyota I have had actually displays trans temp in degrees so in reality most of us have no idea what temps they see under similar use. My diesel trucks have had actual display in degrees F.
What is unique about the 23' TRD Pro I have owned for the last 14 months is
*that in high range it seems to like to climb in a high gear and slip the torque converter.....a lot
*that it actually displays trans temp and that the trans temp bar seems pretty linear and actually moves rather than being very center weighted like many factory gauges that show "in the middle" throughout a wide range of temps. I have never got the overheating warning.
*it is easy to get the trans temp gauge to show "elevated above normal" with slow climbing in high range
*manual shifting will not let you select first gear unless you are stopped or nearly stopped. My driveway is decently steep and it will *not* allow me to climb in 1st gear even at 5 mph unless I come to a complete stop and manually select 1st otherwise it slips the torque converter heavily up the entire 100ft of driveway which just feels weird to me and unlike other Toyotas I have had.

I have towed an 8k Toy Hauler on a 4,000 ft climb from I-70 to Coffee Pot springs and Deep lake in 2wd high and never got overheating light. Had to use 4wd Lo on the way down to keep brakes from overheating (steep switchback dirt road) so it was that steep. Off-roading around Colorado and Utah I used 4wd low in spots it really wasn't needed to keep the transmission from slipping endlessly on the torque converter. Just seemed like the natural thing to do and worked great but I could see lots of situations where it would be frustrating like areas where climbs are separated by stretches of open space where you would have to go back and forth a lot.

Bottom line is they designed it like that, there is nothing "broken" or "wrong" that the dealer can or will fix, and you either have to live around it by using 4wd Lo a bunch or ignore the gauge and see if you ever actually get overheating warning. I am not sure a dedicated trans cooler would do much unless you wired a fan to the cooler that you could turn on for low speed driving.

I can't think of a good reason they designed it like this other than it is very smooth. Maybe they focused too much on getting it smooth and thought nobody uses trucks like trucks anymore.....unfortunately kinda true.

 

No, but my truck came with no external cooler, and like your truck, it is a 6000 lb brick whose Achilles heel is slow speed inclines in 4Hi that create excess heat in its unlocked torque converter.

I added a cooler, but I still don’t use 4Hi in low speed low airflow situations climbing around forest service roads or shelf roads. Low range exists for that situation.

Doing work with an unlocked transmission while in 4Hi at slow speeds is not good for any vehicle. I barely towed with my 4Runner, and I apparently got that 5speed too hot because it started slipping.

At highway towing speeds, you have considerably more airflow, and your torque converter is able to lock up.

A torque converter is a fluid coupler; once it’s locked, the excess heat dissipates very rapidly. As mentioned, you can not lock up at low speeds.

Yes, it’s the Fusion app. I use a Veepeak Bluetooth OBD reader and pair it to my phone.

 

Can you show where you are grabbing those PIDs? I was looking at setting my dash up but couldn't find the A/T data

 

OP, is it possible your previous trucks didn't have a trans temp gauge, so this is the first time you've been aware of it?

Either way, I would just use the manual shift to keep your truck in a proper gear to prevent the torque converter from slipping.

 

10 gears causes more heat than 6 gears due to friction theres no way around it, high stall converters will beat up the fluid in exchange for torque but in the process they generate heat as a byproduct since the system isn't 100% efficient. Same thing with the t case, front dif, and rear dif although not as severe as the torque converter. From what you described it's possible to trigger the overheating light you were driving two axles in high range naturally the torque converter has to give and unlock at times when good acceleration is needed you might've been pulling boost at times which means more fuel at lower afr through the climb oh and we are also cooling the exhaust gas partially with the engine coolant all this generates a lot of heat I imagine you were doing 20 - 30 mph which is where I can't see why it would overheat. But it doesn't surprise any of the members it's been a thing since the release of 22 tundra. Your goal is to reduce the load on the torque converter stay in a lower gear S3-4-5 or use 4lo and D it should help with keeping tc locked. 3rd gens are a little fragile lol we don't the have the girth of a 527 man handling a turbo 400 with the drive axles locked going up a hill at 100 mph so we compromise yes on a $75k truck this is the future according to epa. Trying to not get political but it makes no sense for a country to carry the burden of cleaning the environment when the rest of the world is running catless and burning tires at dumpyards.

 

They are in the purchased pack for your year truck

 

I don't understand why people recommend 4LO when it isn't necessary. Why not just manual shift into a low enough gear to prevent the overheating?

 

Maybe because being in a lower gear doesn't solve the overheating. The non-locked torque converter and gear ratio to overcome cause heat to build up in the torque converter. Switching to 4Lo reduces gear ratio dramatically making it much easier to move the big heavy truck at slow speeds.

 

Interesting. Like the OP, I'm an avid hunter and fly fisherman. I drive my trucks all over the Colorado Rockies. The road in your pic is certainly not what I'd consider 4LO worthy.

That said I haven't had my Gen 3 off-road much, yet. If it can't handle roads like that without 4LO, I may be in the market for a different truck. I'll find out this summer and fall.

 

@SDHNTR

What speed is a slow steady climb ...is it over 15 mph?

 

Locked in OD is what raises temps excessively - unlock the OD so it stays in the highest gear with No overdrive to cause slippage and heat things up. - Same as any other transmission with OD - nothing new.

 

Thanks. But that's pretty disappointing, if 4LO is necessary to keeps temps in check on that road. I get that the pic may not do the grade justice, but that looks like a typical maintained county road in the places I drive.

 

Yes, but by "highway" towing I'm not picturing an interstate. I go camping in the mountains. I'm picturing a two lane, steep and windy mountain pass. You are going maybe 20-40 mph with lots of variability. Sounds like death for this tranny.

 

No, my Dodge had a trans temp gauge. Never got over 200 on same road.

 

OBD Fusion doesn't have trans temp pids for gen 3 yet. They said they're working on them though.

 

Yep, something like that, but several miles long. Not terribly steep, in some spots even less incline than in your pic. I'll try it but 4Lo in any of my previous vehicles would have been totally unnecessary and a real drag to drive up something like that.

 

Bingo! This thing may grow legs soon.

 

OP, you need a trans cooler.

 

I would say in between 10 and 20.

 

I never got the warning. I stopped it before any warning came on, but the gauge was almost pegged.