Max speed in 4Lo?

Whoa, lots of comments on neutral that have me a little concerned . Does it really confuse people nowadays? It kinda sounds like people might think it’s just an outdated vestige from the old-timey days lol.

Neutral isn’t to allow for towing specifically. Or as a safety to keep you from accidentally going into 4L.

Neutral is there because it’s what positively, completely, and mechanically disconnects engine power from going through the transmission and reaching the wheels. Anybody operating a machine with an engine (that runs on its own) needs to have a failsafe way to disconnect it.

Some reasons are operational…like the need to push or tow a vehicle, or various maintanance reasons.

Or the need to shift into 4Lo. The torque converter transmits power at idle. The transfer case comes after the transmission, so neutral physically allows the 4Lo gear to mesh…otherwise it would be like somebody hopping onto a treadmill set to 100mph. Gears would grind and physically reject the 4lo shift if not in neutral.

Neutral is also there to protect life and limb. For example, it can stop floor mats from killing a bunch of people when the decide to attack and hold down gas pedals. In cases of unintended/uncommanded acceleration, literally one very light push forward to N on the shifter lever is all it takes to regain immediate control of the vehicle…with no melting brakes, and no loss of power steering or brakes from shutting down the engine.

 

How is 4hi more “stress” than 4lo?

 

Manufacturers are in a tough spot with any “min or max” recommendations. I mean, at some point, common sense must prevail.

We can’t have people getting t-boned because they were afraid to to step on the gas and exceed 15mph in 4lo.

 

Thanks. Great thread, guys. I’m learning stuff i didn’t know before. It’s also making me realize there’s a lot of stuff I don’t know about how these 4wd systems work. And I’ve been driving 4wd Toyotas for decades.

 

Yup lol. A good way to gain some sympathy for the vehicle is to think about multispeed bicycles. If you need to ride up a steep hill from a standing start, would/could you do it 10th gear? Or 1st gear? Even if you had the power and stamina to start in 10th gear, you’re gonna hurt yourself before long. In this example, your heart and legs represent the vehicles engine and transmission torque converter.

Specifically, 4hi strains the torque converter first. Whenever the engine cant push through a gear ratio, an automatic transmission will allow the torque converter to slip…just like you would slip the clutch on a manual car before the engine stalls out. Except a torque converter is a liquid clutch with no mechanical connection. This fluid coupling is very handy, but it will cause the transmission fluid to overheat when it’s relied on to push power for too long. A two speed transfer case is really a transmission for your transmission….Using 4lo allows the transfer case gearing to do the work instead of the transmission fluid.

However 4lo itself can be rough on the drivetrain components downstream of the transfer case, because the gearing is easily capable of multiplying the force of the engine/transmission beyond the breaking point of axles, CVs and U-joints. If you ever get a tire wedged tight in rocks, or turning, uphill on solid rock, or other situations that physically bind a wheel, and then you goose the throttle too hard…SNAP! It’s a bone-chilling sound….lol. Plenty of youtube videos of snapping cv axles

By the way, I found out I’m heavy enough to break most bicycle chains on command. Put it in 1st, point it uphill, and from a standing start, pull my weight down on the pedal. Easy as breaking a pencil.

 

More on 4ow. I really like this guy's videos, these Australian dudes know what they're talking about, and they have some sweet rigs. Just gaze upon the glory of this 79 series as you watch the video, haha.

https://youtu.be/W4AWMA8YeHU

 

Same. I was doing some off-roading in Vermont back in October, as soon as I got off the dirt main road and onto the rougher section, I just put it in four low and left it there. I don't think we ever exceeded 10 or 15 mph. At one point we were climbing a very steep hill covered in grapefruit sized rocks, I had it in first gear, 4low. I complain about the 4.0 not having low end torque, but with that gearing it climbed that like nothing at 1100 RPM.

@McSpazatron made a great point about the bicycle, that was how I was going to explain it as well but he saved me the trouble.

It's kind of common sense, you just need to have some mechanical sympathy, think about what is best for the vehicle and the terrain.

This is an extreme example, but here is a sick video showing the advantages of low range. This guy has a bunch of other videos, some of them he literally just gets out and lets the truck idle up obstacles.
https://youtu.be/WrRBbh6-eGU

 

So if the wheels are held in place and one applies the accelerator with an automatic transmission, it will heat the transmission fluid and then I am guessing blow the transmission if too much throttle is applied?

 

After a while it could harm the transmission, but the more likely scenario is you break an axle first.

 

I have to say, I always thought 4 Lo was for extreme situations, but the impression I am now getting is that it is more for just general rough terrain, whereas 4 Hi is more for slippery terrain. So for say 6 inches or less of snow on the ground or basic mud, 4 Hi is proper, but for say snow beyond 6 inches or a foot deep, deep mud, and just general hilly/bumpy off-road terrain, always use 4 Lo.

 

I see. I had no idea there is no mechanical connection between the engine and transmission in that sense, that it is a fluid connection. That's a powerful fluid to connect it but also allow it to slip if needed!

 

Living in an area where we average 100" of snow each winter, I think I can answer that. I've driven in snow here for 50+ years and I've yet to use 4Lo in the snow - no matter how deep. Why? Because most of the time, wheel speed is your friend. 4Lo does not give you more traction - contrary to popular belief. And 4Lo does not give you more speed - wheel or vehicle. Now, if I were plowing wet, heavy, deep snow, then I might consider it.

 

Yes that is why I was talking about depth of the snow. I figured snow beyond a foot in particular might strain the drivetrain more to turn the wheels through (when in 4WD) and so 4 Lo might be more preferable. I know 4 Lo can't give more speed as it multiplies the torque and that means less speed.

 

If you're not plowing it, snow depth doesn't come into play. If it's too deep, you'll get high centered and when that happens, drivetrain strain goes down significantly. 4Lo won't prevent you from getting high centered. In fact, it may actually lead to you getting high centered due to inadequate vehicle speed.

 

I see, so thick snow isn't enough to strain the drivetrain where 4 Lo would be preferable? Also I was thinking of like where you would be driving slowly as driving quickly through such conditions could be dangerous. For example a back road with like 1.5 feet of snow and so you drive slower.

 

It seems like you might be trying to assign 4hi and 4lo a little too rigidly. Bumpiness of the terrain has nothing to do with gear selection, neither does mud or inches of snow. Every condition is different, and they may change quickly. So saying use to use X in Y conditions wont always hold true. Gearing is about making the vehicle move weight, or helping to keep that weight moving.

In general, a car wont break because someone thinks it should have been in 4lo when it was in 4hi. But bad habits, or poor understanding of the features at your disposal can eventually put you in a situation where your decisions on the use of the this or that feature can cause damage.

@BlueRunner428 Have you ever driven a manual transmission car? Or a multispeed bicycle? Experience with those can help you understand the impact of gearing, and how it can help or hurt when you pick a particular gear.

edit: i’ll admit, cars are complicated mechanical things. Before being really able to understand whether x or Y is better for a situation, you really do need a basic understanding of what each major vehicle component does and how it does it. Then it’s easier to understand how they can break.

However, Knowing when things will break, that only comes with experience. Sometimes the experience comes from actually breaking stuff. But I prefer to learn by watch other people break stuff, when possible

 

Yes, people were saying though that 4 Hi stresses the drivetrain a lot more, so I was thinking for terrain where it can be more difficult for the drivetrain to turn the wheels, such as bumpy/rutted terrain or deep mud or snow, 4 Lo would be safer...? Have rides a multi-speed bicycle, never driven a manual though.

 

Was it a solid front axle or independent front suspension? I've read that locking the differential with an IFS, if one wheel is sustaining the load (say the other one is off the ground), puts TREMENDOUS strain on the axle components. That lockers for front axles really should only be for solid axles.

 

Just checked on this thread and was surprised it made it to 4 pages. I just wanted to thank everyone for foregoing the “70 mph in 4Lo” comments and instead sharing their knowledge. I learned a ton about the 4wd system and drivetrain in my 4Runner by reading through everyone’s responses and have a much better understanding of how to utilize 4wd in real world scenarios. This is my first 4wd vehicle and I don’t often have opportunities to really utilize it since I live in Florida so the knowledge shared in this thread has been very valuable to me. I’m pleasantly surprised to learn how robust the 4wd systems in these 4Runners are and look forward to gaining experience by putting it to use with the knowledge I gained from this thread.