Open Differentials vs. Traction Control vs. Lockers

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Wolfy

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On a recent group trip we came across a perfect natural experiment to see how OPEN DIFFERENTIALS, LOCKERS, and TRACTION CONTROL handle the same obstacle. I got video of it all and you can see that below. Here are my thoughts on what we saw:

How A Differential Works

Here's the best video I've seen illustrating how a differential works. Check it out:
The Experiment


OK so in a remote canyon in northern nevada, we came across the perfect spot to illustrate how each of these things work. It was a turn through a loose rutted of camber sluice.

It forced everyone into a Cross Axle situation where front passenger and rear driver wheels were up and the other corners were down in loose sand.

Now, because of the way differentials work, this brings even a four wheel drive vehicle right to a stop. So, let’s take a look at how we did.

Open Differentials



In the first clip, David enters the turn and immediately is unable to move forward due to the classic cross-axle on his open differentials. His front passenger is up and the rear driver is up and the other corners are down and mostly unloaded.

The loose sand is just getting flung out of the way and no power is going to the wheels with traction. With a closer look you can see how the rear tire is stuffed and the front is hanging.

In a situation like this there’s plenty of room to re-position and that will keep the vehicle balanced better.

on the new line the problem is still there, but it is less severe and he’s able to finesse his way through.

Let’s back up a second. In the video you may have heard Shawn say, "tap your brakes!"

This is a trick that sometimes works that simulates a computer controlled traction control system.

Traction Control



In the video, Nate drives through the same obstacle in his Tundra with 4-Wheel Camper and suffers from the same differential phenomenon.

But this Tundra has Traction Control. With Traction Control a computer senses that one wheel isn’t getting traction and uses the brake selectively to slow it down.

If you go back to that Explainer vide you can see that the differential uses one wheel as leverage for the other. When one wheel spins without resistance, there is no leverage for the other wheel.

To get past this Traction Control clamps down on the spinning wheel to apply leverage to the other one.

Let’s back up again.

Here’s what I think is happening here with Nate's Tundra. He hits the cross axle, slips, stays on the throttle until the traction control kicks in and now the front wheel is way off the ground and he backs off.

At this point the traction control disengages and he has to start over.
Throttle on, tire slips, traction control engages, truck bucks, throttle off.
As you can see from the difficulties Nate is having here, Traction control is still problematic in a cross axle situation.

Nate was smart to back off before the truck bucked too hard risking bashing into that sand bank, or worse, rolling the heavy vehicle, which is definitely a risk here.

Nate finessed the traction control with low throttle until he got it to engage slowly and smoothly.

Incidentally, almost everyone tended to turn away from the bank here. But the off camber was enough to potentially roll them over. So watch out for situations like this and be mindful.

Lockers



So my 4Runner has a factory installed Electronic Locking differential that I can turn on and off with a button on the dash. This basically turns off the differential so that both wheels turn the same no matter what and they work great in situations like this.

So you can see as I come into the obstacle I immediately lose traction and roll back. So I hit the button and locked the axle. Then, no problem, even though one front wheel is up, the rear has enough traction to push it through. This is a good tool to have because I can use the low gearing and low RPM to just slowly crawl through at a smooth and even pace. No bouncing of bucking.



I’ll show you Ron’s pass in his JK Rubicon just to show that even solid axle vehicles aren’ immune to this either. He spins out same place we did.
Since this is a rubicon, at first I thought he turned his lockers on, but on closer inspection I think this is the Jeep Traction control.

Right there. See how the wheel spins a little and then catches? If you know more about Jeep Traction Control post a comment and let me know what you think is going on here.

Side Note



Now before you go out and weld your diff, you should know that most of the time it’s good to have an open differential. I am constantly locking and unlocking, only using it when I need it. That’s because it can be really hard to turn with the locker on. Watch how the 4Runner is pushed straight with the wheels cranked to driver.
 

Wolfy

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Great post. Jeeps have something called BLD which stands for brake lock differential. There's info on it here.
Thanks!

It’s funny, on YouTube i got a bunch of different conflicting responses on the Jeep traction control. BLD was most frequent though.

Works great either way.

-M
 

Wolfy

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I'll take front and rear lockers over electronic assist anytime. The crawl control on the trd's is pretty nice, very smooth.
Yeah. Me too. However, I think for a lot of what we do, the lockers are either not necessary, or just make thing easier, but you can get by without them with a little creativity.

-M
 

Smileyshaun

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Traction control is okay set up until you actually need some wheel spin or it decides to quit working and makes a vehicle nearly inoperable, the traction control on my Sequoia was so overbearing I eventually just pulled the fuse for it because in snowy or icy conditions the vehicle literally would not drive up a hill without the motor constantly trying to kill power. Personally I would take open diffs over traction control system but everybody is different
 

Wolfy

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Traction control is okay set up until you actually need some wheel spin or it decides to quit working and makes a vehicle nearly inoperable, the traction control on my Sequoia was so overbearing I eventually just pulled the fuse for it because in snowy or icy conditions the vehicle literally would not drive up a hill without the motor constantly trying to kill power. Personally I would take open diffs over traction control system but everybody is different
There must have been something malfunctioning. The consensus I've gotten is that the Toyota system is great.

Personally, I like All Wheel Drive in the snow. At least around town.

-M
 

Anak

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A couple of years ago I finally got my first selectable locker. I added an Ox-Locker in the rear of the XJ. I love it.

When off-roading, as a general rule I will reach for the locker before I reach for 4wd.

BTW, this video is a great tutorial covering the various types of lockers:

 

smritte

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Your analogy's here are pretty close. I will start with this, I prefer selectable lockers for anything past regular dirt roads.

To understand what your seeing, you need to understand how ABS/Traction control actually works. Yes I said ABS.

Ill keep this basic for understanding purposes and only get a little more complicated. All the systems work the same. The differences are software and sensors.

At the wheel you have sensors. These sensors send a signal that is turned into a pulse. As you wheel turns there will be a certain number of pulses per revolution. Lets say 10 pulses per revolution. Each tire will will be the same. With a certain size tire, you will do so many revolutions per mile and the pulses will increase with speed. Now you have MPH and Distance.

Now comes the computer. The computer doesn't care where you are or how fast your going. Its whole purpose is "Make the pulses the same". How it does this is based on software and how many other sensors it can see as well as how many things it can control.

With ABS, it looks at the tire slowing down and makes it speed up by removing brake pressure to that wheel or wheels.
Traction control is the opposite. It looks at the faster wheels and slows them down to the slowest. If the wheels are spinning too fast, it will need to decrease speed by dropping throttle, timing, fuel injection... When the wheels have slowed enough, now it "may" apply a brake by using the ABS system.

Those are the basics. How does yours work? It depends on the manufacture. Most ABS/Traction control is designed for the street. Some for mild off-road. If the vehicle has a factory limited slip and traction control, the ruts in the above pictures should not have been an issue. I don't know but, I would be surprised if someone actually programed in a tire lifting into the software. In all reality, it shouldn't matter. Unfortunately we live in reality, so what was designed, doesn't always work as designed. In the field we called this "undesirable but normal"

Some of the better modern ones will work like this. Slowly pull up on a rock face. Left front tire changes speed slightly (slip). Computer sees this. It gently pulses the left front brake, this moves torque to the right. Now the right slips a little, apply some brake and torque moves back. Doing this it can move torque around as needed. This is why people will tap the brake or slightly pull the park brake for traction. Move torque.

Why doesn't your traction control seem to work? Was it actually programed for off road and what tools was the computer given. For the people who know how these things work, yes I left out a ton of info.

Scott
 
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Arailt

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Traction control is okay set up until you actually need some wheel spin or it decides to quit working and makes a vehicle nearly inoperable, the traction control on my Sequoia was so overbearing I eventually just pulled the fuse for it because in snowy or icy conditions the vehicle literally would not drive up a hill without the motor constantly trying to kill power. Personally I would take open diffs over traction control system but everybody is different
You're thinking of stability control (Vehicle Stability Control - VSC in Toyotas). This is the system in most newer vehicles that prevents sliding sideways and the driver from losing control (i.e., having any fun). It'll also kill power on road anytime the wheels spin too much in general. My GX has overactive VSC as well. It's a real PIA once the roads get slick when it snows. It kills me that there's no VSC disable button like I had in my Tacoma. However, I think most Toyotas auto-disable VSC in 4Lo and/or if traction control is enabled.

What they're referring to here is the electronic limited slip system (TRAC/ATRAC/Crawl Control in Toyotas) that uses ABS to limit slip through the brakes rather than a mechanical LSD or manually selectable locker. To @Wolfy's point, the ATRACII in my GX works really well. This is ATRAC in action on a GX470

I'd still rather have at least one locker though :wink:
 
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Wolfy

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You're thinking of stability control (Vehicle Stability Control - VSC in Toyotas). This is the system in most newer vehicles that prevents sliding sideways and the driver from losing control (i.e., having any fun). It'll also kill power on road anytime the wheels spin too much in general. My GX has overactive VSC as well. It's a real PIA once the roads get slick when it snows. It kills me that there's no VSC disable button like I had in my Tacoma. However, I think most Toyotas auto-disable VSC in 4Lo and/or if traction control is enabled.

What they're referring to here is the electronic limited slip system (TRAC/ATRAC/Crawl Control in Toyotas) that uses ABS to limit slip through the brakes rather than a mechanical LSD or manually selectable locker. To @Wolfy's point, the ATRACII in my GX works really well. This is ATRAC in action on a GX470

I'd still rather have at least one locker though :wink:
I think that's how the Tubndra was working in the video, the problem he was having was the tipping and bucking.
 

Lindenwood

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Traction control is okay set up until you actually need some wheel spin or it decides to quit working and makes a vehicle nearly inoperable, the traction control on my Sequoia was so overbearing I eventually just pulled the fuse for it because in snowy or icy conditions the vehicle literally would not drive up a hill without the motor constantly trying to kill power. Personally I would take open diffs over traction control system but everybody is different
Be careful not to mix up the various traction control functions. On my 2002 3rd gen 4runner, Vehicle Stability Control is there to primarily detect minimize yaw or the potential for yaw. The Trac system primarily worked to detect and control asymmetrical wheel spin.

Together, they actually worked quite well to keep you from spinning out or sliding sideways under hard braking or cornering, which is what the system was designed to do. The VSC would detect vehicle yaw and cut throttle and apply brakes on the outside tires to minimize that yaw. The Trac system would detect wheelspin and use the brakes to stop the spinning wheel.

VSC was only disabled when in 4WD with the center diff locked (i.e. in "full" 4WD, rather than AWD). There, the Trac system still functioned to minimize wheelspin, but the VSC, which was the only system that could actually cut throttle, was disabled.

I still found the Trac system was not nearly as effective as the ATrac on the 5th gen 4Runners, and I got the most gains in capability by softening up the suspension so that the tires stayed more planted in moderately cross-axle situations.

That said, I'd absolutely put modern Toyota Crawl Control on a level playing field with a rig with an open front and a locked rear, as far as pure capabilities go. It is actually quite impressive in the right situations, though it is loud, obnoxious, and overall annoying :P
 
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smritte

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Be careful not to mix up the various traction control functions. On my 2002 3rd gen 4runner, Vehicle Stability Control is there to primarily detect minimize yaw or the potential for yaw.
That's do to being equipped with an Accelerometer. A unit that detects G-Force. Almost all modern traction controls use them. Depending on the build, you can control the traction based on steering input, wheel speed, G-Force, braking and throttle. This is called Torque vectoring. Controlling how much torque a wheel has. If you control this using brakes you get Brake Based Torque Vectoring. This works better will all wheel drive than 2 wheel drive.
Controlling the differentials internally (Differential Torque Vectoring) is the latest technology.
All of your more modern Traction Controls use accelerometer's. Now you can control Yaw, under or over steer, stopping due to weight shift and body roll.
Unfortunately its hard to tell what the manufacture did using their name, acronym or advertisement. They also never agree to use common names on the same technology.

Scott
 

smritte

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That said, I'd absolutely put modern Toyota Crawl Control on a level playing field with a rig with an open front and a locked rear, as far as pure capabilities go. It is actually quite impressive in the right situations, though it is loud, obnoxious, and overall annoying :P
Absolutely agree.
 

Traveler I

Yeah. Me too. However, I think for a lot of what we do, the lockers are either not necessary, or just make thing easier, but you can get by without them with a little creativity.

-M

I forget I have fr and rr lockers...until I'm just spinning the tires, to many years with limited slip diffs. Than it's a face/palm moment, engage locker and drive away.
 

Wawa Skittletits

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A negative with open diffs and traction control not commonly discussed is the added stress it places on the transmission which results in additional heat buildup. A bad thing with autotragics. Coming from a Subaru with open diffs I have what’s called X-Mode which dramatically increases off road ability on technical terrain. I have no issues going cross axles but traction control will obviously never work as smoothly as mechanical locking (LSD or full locking) differentials.
 
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Smileyshaun

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I guess I should have explained what I said a little better, I know the difference in a Trac, vsc , traction control ect ect . im just old school and dont like computers controling what im doing , in some situations and terrain and depending on the driver yes these systems can help with keeping in control . But for me personally and the places I travel in the PNW (wet , muddy ,snowy) I have never found traction control ,stability control or any computer controlled traction aid to work as well as good lines and just enough throttle to keep forward momentum and the tires cleaned out . Give you a good example in my sequoia even in 4 low with the t case locked I was stopped once the snow got to the bottom of the bumper , pulled the fuse for traction control and abs and kept on traveling for 10 more miles till the snow started coming over the hood and I decided to turn around . hdr_00503_0.jpg

But honestly whatever traction aid helps people get out and explore is awesome in my mind. Just be safe and don't rely completely on these systems and know how to turn them off completely if the go haywire ,you dont want to be in the middle of nowhere stranded because a sensor decides to quit working telling the rest of your vehicle it can't move anymore .
 
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Arailt

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Just be safe and don't rely completely on these systems and know how to turn them off completely if the go haywire ,you dont want to be in the middle of nowhere stranded because a sensor decides to quit working telling the rest of your vehicle it can't move anymore .
Very good point. I have no idea which fuse I’d pull in my GX (probably similar to your Sequoia) if my nannies decided to go haywire.