Open Differentials vs. Traction Control vs. Lockers

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.
 

Shovel

Explorer
In many years of sharing trails with others it's become clear that drivers who had to learn proper technique on open diffs are more successful even when they have access to a traction aid; they're paying more attention to tire position and to line selection.

Traction control is reactive by necessity - that takes a different approach than a proactive aid like limited slip or a locking diff. The best success I've had with using traction control is to pretend it's not there and drive like I have open diffs. Pick open diff lines, use great care in commanding just the right speed to carry through without being abusive to the machine or terrain.. and let the traction control step in subtly and smoothly. In contrast, using traction control to force a vehicle through what would be a bad line on an open diff just brutalizes the tires and terrain and brakes.

Newer vehicles which have an enhanced low-speed traction control scheme (like FCA's "BLD") in concert with a mechanical limited slip or locking diff are a pleasure to drive because lines can be chosen based primarily on safety rather than keeping tires planted. Absolutely worth the $$ to insist on that feature when buying new.
 
In many years of sharing trails with others it's become clear that drivers who had to learn proper technique on open diffs are more successful even when they have access to a traction aid; they're paying more attention to tire position and to line selection.

Traction control is reactive by necessity - that takes a different approach than a proactive aid like limited slip or a locking diff. The best success I've had with using traction control is to pretend it's not there and drive like I have open diffs. Pick open diff lines, use great care in commanding just the right speed to carry through without being abusive to the machine or terrain.. and let the traction control step in subtly and smoothly. In contrast, using traction control to force a vehicle through what would be a bad line on an open diff just brutalizes the tires and terrain and brakes.

Newer vehicles which have an enhanced low-speed traction control scheme (like FCA's "BLD") in concert with a mechanical limited slip or locking diff are a pleasure to drive because lines can be chosen based primarily on safety rather than keeping tires planted. Absolutely worth the $$ to insist on that feature when buying new.
Agreed, watching these clips, made me realize that I reach for that locker before trying a better line. Probably better to go for the better line first. I'll be thinking about that in the future.

-M
 

dreadlocks

Well-known member
never had diff locks before, just open and only recently TC/EDL (its disturbing to say the least, you still avoid needing it).. yeah a few times I've thought damn it'd be nice, I wouldn't be stuck right now.. but more often than not I see another fully locked vehicle breeze through an obstacle and think to my self.. well where was the fun in that? I feel accomplished that I conquered some difficult terrain with alot of planning, a lil sweating and great driving, then some rock crawler comes through and makes it look like the big pile of boulders I just busted my ass on was a speed bump and I just move outta their way cuz I'm in no hurry to the finish line.

however, now that I'm expoing further away from home and civilization and not just jeeping in my back yard having the capability in my back pocket would be reassuring, luckily I've not grown dependent on em and know my limits and how to recover w/out em.. IMO If you got diff locks you should wheel w/out em, and like a winch and other recovery gear just try to avoid ever actually using em.. some things are just nice to have, and better to not need.
 

WanderingBison

New member
Fantastic video - what I would love to get more info on is how a traditional/factory limited slip differential or a TruTrack limited slip differential would compare, especially compared to lockers.



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Fantastic video - what I would love to get more info on is how a traditional/factory limited slip differential or a TruTrack limited slip differential would compare, especially compared to lockers.



Sent from my iPad using Tapatalk
Thanks!

My understanding is that they do well as long and both tires have some traction. If one comes up entirely, they don’t work.

-m


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Mundo4x4Casa

West slope, N. Ser. Nev.
I've had a lot of traction aids on 13-4WD rigs over time from a handful of Trac Locs (aka: trash loc) with some messaged; to lunch box lockers; to full Detroit Lockers; to Power Loks (cone shaped clutches under a hefty preload); to full ARB air lockers;

to manual cog locker; to modern Jeep Grand Cherokee selectable traction control; to my 2019 Subaru Cross Trek's X-mode viscous coupling system; to my current favorite, True Trac torque biasing, gear driven limited slips on my RAM pickup's Dana Super 60 front (Dana 70 parts except the housing) and rear Dana 80 diffs. These are also known as a Thorsen design. I also run these under a 1999 Jeep XJ which makes it the best deep snow car I've ever had.
Why do I like the true tracs? Smooth invisibility. Transparent torque delivery. Nothing slips or spins. No wet clutches. No special gear oil. I don't rock crawl with this one, well occasionally, so in order to not tear my Lance camper apart i try to keep the axles untwisted up which also keeps the frame from twisting.

Henderson mentions the tire lifting situation which is not much of an issue with me; at least I've never experienced a problem even after lifting a tire. I still drive like I have no LS or lockers which gives a nice margin of error.
jefe
 

MOguy

Explorer
If you don't understand the added capabilities lockers or traction control offers then you aren't wheeling that hard. I understand many here just run forestry roads where open diffs are fine.

If you off-road enough you will should realize that regardless of the line you pick lockers will help. If you are in areas that get slick your can't always stay on your line.

If you care about the trails you wheel on you should do EVERYTHING you can to limit wheel spin, lockers and traction aids help. Swallowing you pride and using a winch or get pulled though is another option. Driver skill can only go so far. Tread lightly!

Even if you don't care about tread lightly having you vehicle work better will keep you from abusing you vehicle and getting stuck.
 
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craig333

Expedition Leader
Agree completely. In my Jeep the detroit frequently means I don't need to lock in the hubs. Finally got a limited slip installed in the truck.
 

toddz69

Explorer
to my current favorite, True Trac torque biasing, gear driven limited slips on my RAM pickup's Dana Super 60 front (Dana 70 parts except the housing) and rear Dana 80 diffs. These are also known as a Thorsen design. I also run these under a 1999 Jeep XJ which makes it the best deep snow car I've ever had.
Why do I like the true tracs? Smooth invisibility. Transparent torque delivery. Nothing slips or spins. No wet clutches. No special gear oil. I don't rock crawl with this one, well occasionally, so in order to not tear my Lance camper apart i try to keep the axles untwisted up which also keeps the frame from twisting.

Henderson mentions the tire lifting situation which is not much of an issue with me; at least I've never experienced a problem even after lifting a tire. I still drive like I have no LS or lockers which gives a nice margin of error.
jefe
I appreciate your input here with a wide variety of traction-aiding devices used. I've long thought of using True-Tracs front and rear but keep coming back to "ARBs are the ultimate" and probably do better in snowy conditions since they can be turned off. I've had a Detroit in the back of my Bronco for the past 25 years to get through the tough stuff and haven't had a lot of bad experiences in the snow like many report. I like the mechanical simplicity of Detroits and True Tracs. What are your opinions of Detroits vs. True Tracs and do you experience any adverse effects with True Tracs in the snow?

And to the OP - thanks for the videos!

Thanks,
Todd Z.
 

Mundo4x4Casa

West slope, N. Ser. Nev.
Todd, it depends on the vehicle weight and wheelbase. On short, light rigs, of which i've had many, a full Detroit has a large learning curve on ice and snow: when engaged and under load it tries to oversteer in a curve causing handling problems. When letting up on the stupid pedal, it goes into an understeer mode. The sudden shift from A to B can be a woe if you are not used to it. On a slightly angled icy paved road surface with a light rig the rear Detroit or any other fully locked axle wants to migrate downhill, even the slightest angle downhill. I would not have been without my ARB's on my rock crawling CJ-8 above when doing the Rubicon or Hammers. When crawling up over a big rock at an angle, sometimes I would turn off the front one so as not to be pulled sideways. Sometimes I would use front wheel drive, low range (130:1) with only the front ARB locked. Under just the right conditions this was my only option. However, for my purposes with a 10K pound truck camper on ice and snow the tru tracs are my very best option because they bridge the gap between an open diff and a locked all the way across locker. Eaton makes another LS/true locker that has 3 modes: open/LS/full lock. I looked at it and the cross section pic warned me away as it had a LOT of moving parts; a lot more than my simple Tru Tracs. Remember the Tru Trac has gears that worm the power over to the wheel with the MOST traction, not the least like an LS diff. It's that transfer that's transparent and makes you look like a better driver than you are. click still for vid:


Below are Tru Tracs for a front Dana 30HP and a front Dana 60/35 spline:


 

Shovel

Explorer
I really like the manners of a torsen - have only had them on the rear of a vehicle not a front yet - but they become pretty much useless once a wheel is lifted and I've been entirely unsuccessful at making them work any more effectively via brake pedal or parking brake tricks.

After I swapped mine out for a selectable air locker it occurred to me that maybe synthetic GL5 is just too slippery for them to work correctly and I should have tried GL4 synchromesh rated oil to see if it works better.

I'd love to try a front torsen in the future but I already have a clutch operated front LSD.. definitely not worth the work and expense of swapping.

An anecdote from a gentleman who had a front torsen was that they have very good road manners but on extreme low traction surfaces (ice) where both front tires have next to zero traction they will behave like they might as well be a full locker, causing a near absence of steering capability.
 

Joe917

Explorer
Basically open diffs with full manual locking is the best option if the driver understands how to use it.
Traction control is the best for the masses doing the school/grocery run.
Cost and availability by vehicle model are big factors.
 
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