Open Differentials vs. Traction Control vs. Lockers

[roving1]

I have torsen LSDs in three vehicles. I really like them in snowy and overlanding type use. All three of mine respond to left foot braking and or parking brake use to extend the upper limits of performance. I like that they have always predictable performance. Lockers would be nice sometimes but working w/o having to flip a switch is pretty nice just for around town driving even. I just CA t go back to having an open diff all the time even when not wheeling.

I think the fact they go open under no load is also a little easier on the drivetrain than a full locker is, especially for unexpected wheel lift where you are putting a lot of torque down that you don't want to suddenly by accident send all of it through one axleshaft.

At any rate right at the beginning of this vid I am in a truck with twin Truetracs. I have rear cargo leafs cranked way up with no cargo and street air pressure. This is an axle twister section though it is hard to see due to the low angle. My fist two attempts are with no braking and the diffs go open becuase there is no load to bias the torsen gears. On the the 3rd attempt I am applying light left foot braking, maybe 10-15% pedal force and its enough to load up the diff and it walks right up. This almost always works. I've done this with wheels in the air and driven off of jack stands etc. It's not going to get you up ledges or going to work in a situation where you need a really high torque input but it works in a lot of situations.

Video

Somebody really needs to make a selectable locking diff that is LSD the rest of the time and then we would all be in heaven.

 

[Happy Joe]

Somebody really needs to make a selectable locking diff that is LSD the rest of the time and then we would all be in heaven.

Also that is what Jeep Rubicons (at least mine) came with); Torsen style selectable locking differentials... not impressed!
Their construction and internal parts do not inspire confidence....when; not if, they break ARBs are going in.

Tried a Torsen in the front of the, at best, moderately capable, Explorer; It is OK, for street, highway and maintained roads but I would rather use a (foot in this case) switch to activate and not rely on trying to convince it to do its job by using the brake peddle.... The explorer has an ARB in the rear. The all terrain (street) tires and IFS really conspire to keep it on roads.

I have suspected that electronic traction control plus Torsen style L/S differentials might be a good combination for the less experienced.

Have tried most types of limited slips and more than a few "lockers"... ARB is the winner in my book "When the going gets tough enough to actually need a locker..."

Enjoy!

 

[fawndog]

That is not a locker, it's a LS designed to put more pressure on a clutch pack, and when the clutch pack wears out you get neither.

 

[TernOverland]

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.

Well done Mike! This is a very nice demonstration for those unfamiliar with these systems in real applications. I'm going to save it so I can refer people to it. I learned to drive offroad in a Baja VW, so I'm pretty obsessive about line picking and throttle control. I rarely use my lockers, or even 4WD since my transfer case can select 2Lo. None the less, after 46 years in the saddle, I won't have a vehicle without selectable lockers front and rear. When you need then, you really need them, and I got tired of digging a long time ago.

 

[roving1]

I may be super out of the loop what Jeep ever came with a Torsen/Helical gear LSD?

 

[roving1]

That exists.. https://aftermarket.auburngear.com/ected-max.html?limit=all

Should have specified helical gear LSD. My bad

One thing some people forget with ARB's is it is hard to use them and turn at the same time. Being able to turn with pseudo oped diffs that only lock when you are losing traction can be pretty handy. I drove the Morrison Jeep trail in my truck and literally just walked up the whole thing without unlocking and locking the diffs over and over due to the never ending switchbacks.

In my case I really thought about ARB's but I really didn't want to futz with onboard air. There is always someone somewhere with a leaking ARB that won't engage.

I thought about e lockers but for my application one e locker was more than 2 TT LSDs AND new ring and pinions would be so I just could not justify it.

If all you care about is rock crawling I definitively think lockers are great. But I think people sometimes are not accurate in accessing what they really need and don't understand the real pros and cons between helical LSD's and true lockers. I say this from the experience of being a delectable locker or locker guy for decades before running helical LSD's. The amount I need lockers is less than the amount of time I want to drive around with an open diff, which is none including pavm,ent

 

[Happy Joe]

Should have specified helical gear LSD. My bad

One thing some people forget with ARB's is it is hard to use them and turn at the same time. Being able to turn with pseudo oped diffs that only lock when you are losing traction can be pretty handy. I drove the Morrison Jeep trail in my truck and literally just walked up the whole thing without unlocking and locking the diffs over and over due to the never ending switchbacks.

In my case I really thought about ARB's but I really didn't want to futz with onboard air. There is always someone somewhere with a leaking ARB that won't engage.

I thought about e lockers but for my application one e locker was more than 2 TT LSDs AND new ring and pinions would be so I just could not justify it.

If all you care about is rock crawling I definitively think lockers are great. But I think people sometimes are not accurate in accessing what they really need and don't understand the real pros and cons between helical LSD's and true lockers. I say this from the experience of being a delectable locker or locker guy for decades before running helical LSD's. The amount I need lockers is less than the amount of time I want to drive around with an open diff, which is none including pavm,ent

IMO its personal preference; turning has never been a problem, for me, because the ARBS are unlocked until I need them;. Trying to do snowy/slippery side hills or interstate highways with black ice with non-selectable/automatic/Detroit or lunch box lockers can be white knuckle time, especially in a short wheel base vehicle... used that t-shirt to wax the Jeep.

I typically switch the front ARB on or off using an old style dimmer switch under the carpet, for hands free operation with automatic transmissions, with manual transmissions I install the old style floor dimmer switch to control the head lights and use the bright dim on the turn signal to control the front ARB.

...Just another Opinion (and most stink, I know) but if its not necessary to, at least occasionally, air down for traction/flotation the trail probably doesn't justify/need lockers...

Enjoy!

 

[Mundo4x4Casa]

Henderson, after reviewing your informative vid on traction aids for cross axle conditions, I would add some fringy items to your fine piece.
*One is the softness and articulation (aka; range of motion) of your springs whether leaf or coil.
*Another is the weight or lack of in each situation.
*Another is whether you disconnect your anti sway bars to add more articulation and have enough unimpeded travel (fender clearance and longer brake hoses). Here's the resulting articulation due to these items in the Little Sluice about 2004:
<a href="http://s194.photobucket.com/user/jefe4x4/media/FourWheelDrives/Jefe2 little sluice CJ-8.jpg.html" target="_blank"><img src="http://i194.photobucket.com/albums/z240/jefe4x4/FourWheelDrives/Jefe2 little sluice CJ-8.jpg" border="0" alt=" photo Jefe2 little sluice CJ-8.jpg"/></a>

I notice the Tundra had rather limited flex even with the camper on the back pushing down on the suspension. With 8 leaves on the rear of my RAM (5 on the main pack and 3 on the upper overloads) I should have less flex than the Tundra but I think it may be more:

and: click to open vid: This is going up the great sand drop off in Anza. To be clear, on this day in March my bro John tried this in his 1999 F-250/rr LS/ diesel/OUTFITTER! @ 30 pounds of air in 3rd gear/low. He didn't make it. TP too high (not enough floatation) and not enough momentum. About 1/2 way up he sank to frame and had to slowly back down keeping perfectly vertical. It was now my turn. After his experience he bade me lower my pressure to 20 pounds (just about bottom for a 10K pound truck camper even with wider super single wheels) and try the first part in 4th gear/low range. Near the top I downshifted to 2nd gear to get across the deep moguls. We both have 6 speed manuals. I have True Tracs front and rear which held fast through the moguls.
https://www.dropbox.com/s/bfj5y93wsd7vfkw/jefe does sand hill at dry wash of the devil Anza.m4v?dl=0
I notice a variety of outlooks on this thread, all based on their personal experience. It's a stretch to compare each situation as equal. I do not go looking to twist my axles up as that twist will transmit to the frame and truck bed and try to tweak the camper's frame, in essence trying to pull it apart. I avoid this at all cost, changing to a different line than normal off roaders would try. People in Jeep JK's would not have this worry.
jefe

 

[Dalko43]

One thing some people forget with ARB's is it is hard to use them and turn at the same time. Being able to turn with pseudo oped diffs that only lock when you are losing traction can be pretty handy. I drove the Morrison Jeep trail in my truck and literally just walked up the whole thing without unlocking and locking the diffs over and over due to the never ending switchbacks.

In my case I really thought about ARB's but I really didn't want to futz with onboard air. There is always someone somewhere with a leaking ARB that won't engage.

I thought about e lockers but for my application one e locker was more than 2 TT LSDs AND new ring and pinions would be so I just could not justify it.

If all you care about is rock crawling I definitively think lockers are great. But I think people sometimes are not accurate in accessing what they really need and don't understand the real pros and cons between helical LSD's and true lockers. I say this from the experience of being a delectable locker or locker guy for decades before running helical LSD's. The amount I need lockers is less than the amount of time I want to drive around with an open diff, which is none including pavm,ent

That turning issue is not limited to ARB's; all on-demand lockers (ARB's, e-lockers) have that issue. Engage the lockers on when you need them and disengage them once you've gotten through the limited traction situation. They're not designed for long duration driving.

As for whether or not true lockers are needed by the masses...I'd say that's subjective. However, most OEM's put them into their hardcore offroad models for a reason. I've only had to use my lockers a handful of times, and I obviously don't find them useful on street driving (even with snow or otherwise low traction). But for those few times, they were absolutely essential and limited slips or brake-traction systems would not have worked.

Lockers are sort of like life jackets...very expensive life jackets. You'll rarely need them, but when you do need them, they'll mean the difference between success and failure. Any 4x4 build that is being geared towards self-sufficient overland or hardcore offroad applications should have a locker IMHO. Limited slips and traction systems (as good as they are) are incomplete solutions to a very rare but difficult problem.

 

[MOguy]

Should have specified helical gear LSD. My bad

One thing some people forget with ARB's is it is hard to use them and turn at the same time. Being able to turn with pseudo oped diffs that only lock when you are losing traction can be pretty handy. I drove the Morrison Jeep trail in my truck and literally just walked up the whole thing without unlocking and locking the diffs over and over due to the never ending switchbacks.

In my case I really thought about ARB's but I really didn't want to futz with onboard air. There is always someone somewhere with a leaking ARB that won't engage.

I thought about e lockers but for my application one e locker was more than 2 TT LSDs AND new ring and pinions would be so I just could not justify it.

If all you care about is rock crawling I definitively think lockers are great. But I think people sometimes are not accurate in accessing what they really need and don't understand the real pros and cons between helical LSD's and true lockers. I say this from the experience of being a delectable locker or locker guy for decades before running helical LSD's. The amount I need lockers is less than the amount of time I want to drive around with an open diff, which is none including pavm,ent

If you have a locker it will make it harder to turn, even automatic lockers will. By having a selectable locker you can turn it off when that is an issue. If need be you can keep the rear on and turn off the front. This will make it easier but not as easy as open. There are times this maybe an issue and you may have to do a little back and forth but you still can make it. Everything has its advantages and disadvantages.

As far as leaking. Mine have leaked twice since I installed them in 2001. One time was a 5 minute fix, the other is within the front diff. Not bad for almost 18 years of service. On board air is good to have.

People talk about the Torsen. The HMMWV uses them and I had them in my 4Runner. They work well with brake modulation, not like locker but they may be more than adequate for many.

 

[SnowedIn]

Lockers are sort of like life jackets...very expensive life jackets. You'll rarely need them, but when you do need them, they'll mean the difference between success and failure. Any 4x4 build that is being geared towards self-sufficient overland or hardcore offroad applications should have a locker IMHO. Limited slips and traction systems (as good as they are) are incomplete solutions to a very rare but difficult problem.

I very much agree with this - I spend a lot of my time offroad solo, and having a locker for self recovery (in conjunction with Maxtrax) is the difference between 5 minutes of work to get unstuck and an hour.

There are also a few places I go frequently that some vehicles can't even get into without a locker (getting back out is fine).

 

[Happy Joe]

If you have a locker it will make it harder to turn, even automatic lockers will. By having a selectable locker you can turn it off when that is an issue. If need be you can keep the rear on and turn off the front. This will make it easier but not as easy as open. There are times this maybe an issue and you may have to do a little back and forth but you still can make it. Everything has its advantages and disadvantages.

As far as leaking. Mine have leaked twice since I installed them in 2001. One time was a 5 minute fix, the other is within the front diff. Not bad for almost 18 years of service. On board air is good to have.

People talk about the Torsen. The HMMWV uses them and I had them in my 4Runner. They work well with brake modulation, not like locker but they may be more than adequate for many.

The people that I run with that have front Detroit lockers like them because they unlock one wheel automatically in turns (especially handy for those without the presence of mind to switch a selectable locker off)...I am an ARB fan.
Unless the Detroit locker is broken a person should not experience increased effort turning. ...cant really talk about other ratcheting lockers. The lockers in our crew are ARB's, Detroits and one set of (two front) Unimog portal axles. If just going camping my explorer has a front Torsen L/S (couldn't get an ARB for it); fine for semi maintained roads, IMO; however the fact that you have to mess with the brake to get full traction off road, is a HUGE down check/black mark against them and true tracks, IMO).

Enjoy!

 

[gwittman]

I drove a 1973 FJ55 Landcruiser off-road for nearly 15 years in all kinds of rough terrain with open differentials. Much of it was around Moab and Death Valley. The only time I got stuck was in Anza-Borrego when a washed out, 3 feet deep trench collapse and I fell into it. Once I managed to crawl out of the vehicle and accessed the situation I was surprised it didn't roll on its side. I got out my shovel and dug ramps for the front and rear tires that where way down in the trench. I then got in and drove right out of the trench. Lockers or LSD would not have done it better.

As has been noted before, taking a good line in rough situations makes all the difference in needing better differentials or not. I was probably pretty lucky back then too. My wife and I would head out for 5 day trips by ourselves and sometime see no one for days. We did check in and sign log books at Ranger Stations when we could just in case we had problems and could not come back out. I learned how to drive a good line out of necessity because I couldn't afford upgraded differentials and it was hard to find anyone that wanted to go to the places we did back in the 70s and 80s.

Now, I have the upgrade differentials just to make things a little easier and I can afford them. Too bad the wife didn't stick around to enjoy them.

 

[nickw]

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:

I'm with Mundo here - any sort of auto locker is a big liability in many (not all) ice or snow situations. I was wheeling with a buddy in his Cherokee years ago w/auto locker in the back, tight 2-track road in the woods, slightly offcamber uphill, we went down ok.....but coming back up, we lost traction and the rig was sliding sideways 6" every time we would attempted to move forward / apply power. There was a 50' cliff on the side of the road. It's something a subaru / audi / any SUV could have made it up no problem. We were stuck in a sketchy situation. We wheeled all day with no problems in the snow but were screwed here.

I've also been in situations here in Oregon on some of paved highway passes where I've had to come to a stop around a tight bend / slight offcamber due to folks spinning out. I'd envision the same issues trying to apply power here also.

Things are obviously different in the SW, but anyplace where there is ice/snow, selectable is where it's at IMO.

 

[Photomike]

I do not do much if any trails in a year so my experience is on the road. I do end up driving in daily conditions that most people don't drive off road in. A foot or more of snow, ice covered roads, muddy roads and debris covered roads. I also do not drive a 4x4 for various reasons. I have three vehicles that I use:

• My daily driver a 2010 Dodge Journey with traction control
• 2012 Ford E350 19' motor home with traction control
• 2017 Ford Transit with traction control and LSD (limited slip differential)

My biggest issue with all three is how they each handle the different situations so differently. The Dodge being front wheel drive has all the advantages of the front wheel drive but the TCS makes it annoying to drive on anything but basic wet roads. Add anything more than water on the road and the traction control goes nuts. Even if you are successfully moving through something like a foot of snow. The second it detects any slippage it starts the braking and you loose forward momentum. Switching the TCS off helps but it seems that it still is there and will intervene if it thinks it is bad enough. Again usually at the worst time when you are moving it jumps in for a second to try and help. The motor home seems to be the best with switching off the TCS but I think this has to do with how much weight is on its back. The extra couple thousand pounds gives more drive and momentum and reduces slipping till you are actually stuck. Then you can deal with it and the TCS does not seem to cut in The Transit is a mix of the two. On a road with a little water/snow/ice the TCS is great on the Transit. Start to slip and it corrects. If you are in something major the TCS again looses its mind and cannot seem to decide what you want. You get moving and a little slippage and you are slowing down. Taking the traction control off and things are better with not loosing forward momentum BUT your back end is at risk of wiggling all over the road so you have to stay alert to if the system is on or off to drive accordingly. As for the limited slip I am not sure where or when it works so I am not leaning on it to help. I added KO 2's to the Transit and more weight and it does seem to help a lot. Again more like the motor home in having some weight to cut through stuff.

In my world at least I would prefer a TCS that I could disengage 100% when I am in something I am driving for and know that it is off and will not come on for any reason. And I would like lockers that I could hit a button and know 100% they are on. I got the LS on the Transit as it came with it so was not here or there.