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

If it doesn't need 4WD then there is no problem. If it does need 4WD, but is under 15-20 MPH, then 4LO is the answer.

 

Sensible response. You are correct on all counts.

 

Bingo!

 

For one it doesnt have that dog crap 3.52:1 first gear they graced us with in the A750/A760 transmissions. It has nearly a 5:1 first gear. That should help a lot low speed. But somehow doesnt.

 

Because it's loose dirt. And because I am looking for game and being aware of my surroundings while hunting and don't want to haul ass. And I don't want or need low gearing that 4Lo provides. Go slow on loose dirt roads with a mild incline and you slip tires. Put it in 4Lo and it's unnecessarily loud and unpleasant to drive. 4H and a capable vehicle is the answer, as it always has been in the past for me with every other vehicle. Unfortunately, and apparently, that's not a capability of the 3rd gen Tundra. Case closed.

I guess some people just don't understand these driving conditions. I'm done with this thread.

 

I really think the issue is not having an air cooler that is getting air pulled through it by the main engine fan. At slow speeds you are likely not getting much coolant flow through the thermostat since the engine is not working hard and producing much heat.

 

I get it and I think the 4Auto on the Big 3 solves your problem. The Tundra does not have this feature because Toyota has never made it in North America that I am aware of. They have full time 4wd which is way better than the Big 3 plus Jeep 4Auto - but full time 4wd affects mileage by 1mpg. The new Tundra had to meet mileage targets.

 

Unfortunately, with the 3.31 gears in the axles of the Gen 3 that 5:1 first gear only results in a slightly higher (numeric) final drive ratio.

 

Not really related to the thread, but they just put full time 4wd or auto 4wd (can't remember which) in the new Tacomas.

 

Its 25% higher numerically even with the 3.31's. Thats not slightly higher.

That is 100% why I bought a 2016+ Land Cruiser with the 8 speed, because the 6 speed in the 2nd Gen Tundra has an even taller 1st gear than the 4Runner. Everyone with 2nd gens loves to brag about their 4.3 axle gears, completely ignoring the fact that their 1st gear is a 3.33:1

 

Only in the limited trim though. same with the 4Runner. The only ones getting full-time across the board are the Land Cruiser, GX550 and LX600.

 

Im not sure how 4Auto would save his transmission from overheating though. 4Auto is basically just running in 4Hi but allowing some slip on the front axle.

While I agree that the full-time Torsen t-case found in other Toyota's is awesome for the scenario he describes it doesn't let the transmission run any cooler. I rarely locked up the center diff in my GX460 offroad unless it was really hairy. Even lifting tires it would pull through.

 

Hmm...not sure about your math. A 3.52 first gear with a 4.30 axle ratio is a 15.1 final drive ratio. A 4.92 first gear with 3.31 axles is 16.3. That's about a 8% improvement, if my math is correct.

 

he asked about his 4Runner which has 3.73's. And the 4.6L Tundra with the A750/A760 only came with 3.91's I believe..

The 5.7L Tundra's 6 speed has a 3.333:1 1st gear, even worse. The Land Cruiser with the same 6 speed had 3.91's. Their stock crawl ratios are pretty terrible.

Its why people can drop 35's or 37's on the new Tundra and it doesnt even care. With 37's the new Tundra's gearing is equal to the stock 2nd gen on stock tires.

 

Yes the Tacoma now has full time 4wd.

 

4 Auto is 2wd and your front diff goes for a ride. Its not engaged no drag/minimal.
When slip happens the fluid becomes viscous and engages the front diff.
So the temps would be just like in 2wd or close. I am assuming here. Have had many vehicles with 4auto.
But not in his scenario. Long heavy pull up - long distance on gravel road.
I believe Toyotas full time system would be fine. I have it on my 4Runner and have never had to lock up either - unless it was for kicks to keep it lubricated. You can't go wrong with any vehicle that has a Land Cruiser 4wd system.

 

Yes, only the limited, but I was just letting him know because he said that it wasn't in NA to his knowledge.

 

It would be in RWD majority of the time. Only engages when slip is detected

 

That is not how 4Auto works in Ford or GM trucks. Ram's I know less about but know they also use a Borg Warner case like GM/Ford so i assume its probably the same.

My F150's 4Auto was active all the time, sending power to the front axle even in a straight line on dry pavement. The hubs would engage as soon as you went into 4Auto and then the t-case would vary the clutch pressure on the fly.

 

My GM worked as borla described in 4Auto, didn’t activate until the rear wheels slipped. So, the Ford acts like AWD when in Auto…aka 4H?

 

@mass-hole
Words and terminology.
Its active in that it will kick in "auto" matically when selected. Its in rear 2wd in normal mode.
I can tell you that a family member with a F150 and Sierra both with 4Auto last summer, told me that the GM system was faster kicking in to the front when coming into the trails.
Meaning he sensed a little slip with the Ford. Subjective.

 

this^ , tons of people miss that fact.

 

so the cooler from say the LC500 would not be a feasible option?

I’ve been looking around seems the LC500 or even the LC350 may have a good cooler option similar transmission?

Something like this perhaps?
https://lexusboutique.net/products/...-is-500-automatic-transmission-oil-cooler-kit

 

All of my low speed off-roading has been with skids. Adding the external cooler dropped temps significantly. My drivetrain, which granted is different than yours @SDHNTR, has greatly benefitted from the external cooler.

The internal oil cooler puck in my transmission is still working to make the transmission fluid track engine oil temps. So it works against the external cooler *up to* the temp of the engine oil.

The main benefit is that I have something now that keeps temps from running away from that internal oil cooler puck.

This is with engine and transmission/cat skids.

 

Given the current quality issues many of the Big 3 are suffering with, I would strongly consider installing an aux cooler (properly) before taking a loss on a new truck by selling it, especially if this is the only issue with the truck. If there are others, that may be a different story.

We personally have nothing but headaches with our GM's here at work.

 

Wrangler folks are halving the same issue.

"I just had the same scenario a few weeks ago. I was in 4 Auto going slowly and the same message came up. Trans temp was at, I think, 240 something. I switched to 4 Lo and the temp went back to around 180. I just went to 4 Lo whenever there was a stretch of slow, high effort wheeling and didn't have any issues the rest of the day."

 

Interesting. I had two Cherokees with 4Auto. Jeep has been making 4 Auto going back to the 80's.
4 Auto is best for varying conditions. You can set and forget. It will bring on the front diff as needed.
But if you are on terrain best suited for 4 Hi, 4 Auto will work but it will always be "on", so the drag will still be high like 4 Hi.
You might as well use 4 Hi which will have better grip, and then go to 4 low if needed. JMO

 

The Fords can vary the torque to the front axle anywhere from 0 to 50% on the fly. It’s not on or off.

It’s called the Torque on demand transfer case and ford has been running it since 2012
https://www.borgwarner.com/newsroom...-wheel-drive-transfer-case-for-the-ford-f-150

I don’t know what year GM you had but their trucks have had the same system as ford since at least 2019.

 

I’m not even going to argue. It’s not worth it. I posted a link if you wanna read it. Fords been running and “active awd” 2 speed t-case since 2012. It does what I said it does.

 

Do you think the Ford 150 transmisson and the way it is programmed (gearing), will also heat up like the Tundras in these conditions?
Forcing 4wd Low running. Long uphill slow climb 15-20 mph, loose gravel, pulling a heavy load.
or.. the OP should rent a F150, GM or RAM for the weekend and find out for sure.

These 4wd systems are old. The only thing complicated about them is the marketing. For Pickups breaking the systems down into the basics helps.

2wd - Rear, 4 Auto, Part Time 4wd (4Hi/4Lo), and Full Time 4wd (i.e. Torsen based system - New Tacoma)
*****
AWD term used alot is for cars suvs vans (Sienna)