Open Differentials vs. Traction Control vs. Lockers

[Metcalf]

I believe it was an old school/original design, Detroit Locker (not the soft locker)...It was in the '81 CJ-5... note; the soft locker is/was much more "civilized" but can still be a handful...was in the front.
One of my friends made it (the -5) into a rock buggy, on 38s, and he, too, tended to go more sideways than forward on slippery (packed snow and ice) side hills (with ARBs, unlocked, I was able to get across only having the rear slide downhill a little..

Enjoy!

So it was an auto locker in BOTH ends?

I am trying to differentiate the issues of a REAR automatic locker. I think a lot of people conflict that.

I've found the newer soft locker design to be more problematic when used in the front. It helped when used in the rear axle to make things a little smoother and less clunky. Once I figured out that with the rear end open ( or limited slip or selectable open ) that generally ALL the bad habits of the auto-locker in front went away, I actually wish the old detroit locker design was still available commonly. It seems to like to lock/unlock a bit easier without the extra stuff in it. The Yukon Grizzly seems to be a good alternative.

 

[Buliwyf]

The Yukon Griz will be my next front locker. (new truck)

You can remove a couple of the Detroit Soft locker parts for front use. It won't be as soft then, but it'll unlock easier. I forget which parts exactly.

Front Detroit or Yukon Griz, and rear selectable, is all the rage, over here.

 

[Metcalf]

The Yukon Griz will be my next front locker. (new truck)

You can remove a couple of the Detroit Soft locker parts for front use. It won't be as soft then, but it'll unlock easier. I forget which parts exactly.

Front Detroit or Yukon Griz, and rear selectable, is all the rage, over here.

I keep trying to tell people.

I currently own both systems. My flat fender is auto front and selectable rear. My LX45 is selectable/selectable.

My next build will be automatic front and selectable rear.

 

[Happy Joe]

So it was an auto locker in BOTH ends?

I am trying to differentiate the issues of a REAR automatic locker. I think a lot of people conflict that.

I've found the newer soft locker design to be more problematic when used in the front. It helped when used in the rear axle to make things a little smoother and less clunky. Once I figured out that with the rear end open ( or limited slip or selectable open ) that generally ALL the bad habits of the auto-locker in front went away, I actually wish the old detroit locker design was still available commonly. It seems to like to lock/unlock a bit easier without the extra stuff in it. The Yukon Grizzly seems to be a good alternative.

I really did not like the sudden lurch and loud bang of the original Detroit locker in sharp corners (when driving a bit too fast)
Yes, before getting rid of the 5 I ran a autolockers in both ends.
Before I put the soft locker and D44 Scout axles in the CJ-5 I ran a Narrow, D30, ARB front with the original Detroit in a D44, narrow rear; it worked fine in the snow, only sliding sideways (downhill) when locked in on very slippery surfaces and on the interstate, and in town on hills in 2wd on black ice (even slippery-er surface).
When shifting to the scout axles I transferred the original Detroit from the narrow, flanged 30 spline (mail jeep) D44 to the scout D44.

After going to a longer wheelbase CJ-7, it (largely) stopped trying to kill me on black ice on the interstate; so I blame most of the homicidal tendency on the shorter CJ-5 wheel base. I really didn't see much difference when going to 2 auto lockers (other than not being able to turn one off for snowy side hills.. With 2 auto lockers or an ARB front, locked, and an autolocker; the results were similar). The main advantage of the front auto locker was that I didn't have to remember to turn it off after an obstacle; the main disadvantage of the auto lockers was that I could not turn them off. The auto locker in front allowed me to turn just find on high traction surfaces like Moab, not really possible with a front ARB when locked. On medium traction surfaces I could turn (but not sharply) with the ARB locked. To turn sharply with the ARB I really need to turn it off....

A hydraulic power steering booster ram, installed when I went to the wider Scout axles, helped ease the steering effort. Before installing the ram power steering boxes did not last well.

I also noticed that the wider axles did seem to have less tendency to jump sideways at the peak of the corner on steep, very curvy, gravel roads (when going too fast).

Enjoy!

 

[Metcalf]

I really did not like the sudden lurch and loud bang of the original Detroit locker in sharp corners (when driving a bit too fast)
Yes, before getting rid of the 5 I ran a autolockers in both ends.
Before I put the soft locker and D44 Scout axles in the CJ-5 I ran a Narrow, D30, ARB fron with the original Detroit in a D44, narrow rear; it worked fine in the snow, only sliding sideways (downhill) when locked in on very slippery surfaces and on the interstate, and in town on hills in 2wd on black ice (even slippery-er surface).
When shifting to the scout axles I transferred the original Detroit from the narrow, flanged 30 spline (mail jeep) D44 to the scout D44.

After going to a longer wheelbase CJ-7, it (largely) stopped trying to kill me on black ice on the interstate; so I blame most of the homicidal tendency on the shorter CJ-5 wheel base. I really didn't see much difference when going to 2 auto lockers (other than not being able to turn one off for snowy side hills.. With 2 auto lockers or an ARB front, locked, and an autolocker; the results were similar). The main advantage of the front auto locker was that I didn't have to remember to turn it off after an obstacle; the main disadvantage of the auto lockers was that I could not turn them off. The auto locker in front allowed me to turn just find on high traction surfaces like Moab, not really possible with a front ARB when locked. On medium traction surfaces I could turn (but not sharply) with the ARB locked. To turn sharply with the ARB I really need to turn it off....

A hydraulic power steering booster ram, installed when I went to the wider Scout axles, helped ease the steering effort. Before installing the ram power steering boxes did not last well.

I also noticed that the wider axles did seem to have less tendency to jump sideways at the peak of the corner on steep, very curvy, gravel roads (when going too fast).

Enjoy!

Now we are getting some of the details to come out.

What I am generally most concerned about is what I call '3-wheel drive' performance. What happens when you need more than open/open and less than locked/locked. I find this to be the area most people overlook. For me, it is where the most maneuverability of the vehicle needs to be maintained BUT you need more traction than open/open can provide. If you are locked/locked it generally maneuvers like crap no matter what lockers you have.

-What I have noticed.

1. If only the rear axle is locked, it doesn't matter if it is an automatic or spool, the vehicle will be pushed through the turn wider. The rear tires always want to push the vehicle straight ahead. The front tires are pushed off things more often when trying to maneuver.

2. If only the front axle is locked, contrary to what most people seem to think, the vehicle will turn tighter ( in 3wd ). Yes, an open/open vehicle MIGHT turn a wee bit tighter in some situations, BUT we are talking about being in a situation where open/open isn't enough traction. A locked selectable ( a spool basically ) will be harder to steer because of the typical scrub radius, but that is a steering force issue, not a vehicle maneuverability issue. The automatic front locker, when used alone, has LOWER steering force than the front selectable when locked. I think this is because the steering action scrub radius can actually force the locker to ratchet and eliminate any bind in the system. With only the front locked, and the front tires pointing in the direction you want to go, the vehicle tends to stay on line better. This is especially true when trying to climb and turn at the same time.

3. The biggest issue I have with a front selectable locker is getting it to UNLOCK when I want. I think this is the tragic downfall of all the existing selectable locker designs on the market. Once locked and bound up, they do not want to unlock. This is especially true when used in the front. Unlocking the REAR locker first seems to help eliminate some of the bind front to rear, but the front locker always takes longer to unlock typically.

This is why I tend to lock the FRONT locker first and only toggle the rear locker on/off as needed. If you want to use selectable lockers this way, it is best to have extra steering force available with a hydro assist system if you have large tires. With a front automatic locker, it basically eliminates the need for hydro assist steering in a lot of cases. If you are running HUGE tires you will eventually need some more steering force available.

 

[Happy Joe]

For me, in the CJs I only noticed the rear auto locker on normal surfaces while driving very aggressively (too fast/hard) (other than a few rare issues like sometimes going into free fall on some very steep very mogully down hills..
...Thinking back i did notice some front not sticking to rocks where I wanted them issues, occasionally, although I never thought to blame the rear Detroit; its a definite possibility.

As far a tightness of turning when locked on most surface i found that the locked ARB front prevented tight turns (likely because it acts like a spool (preventing the differential from acting as a differential) when engauged, and the higher the traction/lower the tire slippage, the more that it did so. especially when both rear tires had good traction; potientially causing the whole driveline to bind ... Note that most of the time the front tires were prevented from turning to their limits by tire interference with the frame.
That said when both rear tires had superior traction and one front tire hit a patch of sand, in 2wd. the friction of one front tire trying to turn was, some times, not sufficient to force the rear Detroit to ratchet/release one tire.. resulting in it pushing the front ties side ways instead of turning... put me in the other lane several times; usually in the spring due to sand on the road.

With the soft locker in front I don't remember any excessive steering effort.. it was some years ago now (the ram was installed due to the locked ARB steering effort and its affect on steering box life...it, likely, was unnecessary with the soft locker and only slightly necessary with the 12.50 x 35 inch tires, it did help, noticeably when running the wider much higher traction Boggers though).

With the ARBs that I have had (IF I can remember to turn the front one off (embarrassing))... a slow back and forth with the steering wheel while moving is normally enough to let them release after driving over an obstacle (very similar to getting some old school locking hubs to disengage after a trail run)... occasional drive line binding is , IMO, just going to happen in solid mechanical drive lines.... I don't see it changing until independent electric 4wd becomes common and eliminates a direct mechanical connection between the wheels..

Being lazy, and no longer even trying the semi extreme/very difficult (body damaging) trails any more I just lock the rear at at the trail head on most (not Moab/medium traction or lower) terrain then lock the front in just before the obstacle and unlock it after...I only unlock the rear mid trail (very rarely) if I feel a tire bind and slide, momentarily; as the drive line unwinds (eventually I expect the binding to break a transfer case drive chain).

Enjoy!

 

[Metcalf]

For me, in the CJs I only noticed the rear auto locker on normal surfaces while driving very aggressively (too fast/hard) (other than a few rare issues like sometimes going into free fall on some very steep very mogully down hills..
...Thinking back i did notice some front not sticking to rocks where I wanted them issues, occasionally, although I never thought to blame the rear Detroit; its a definite possibility.

As far a tightness of turning when locked on most surface i found that the locked ARB front prevented tight turns (likely because it acts like a spool (preventing the differential from acting as a differential) when engauged, and the higher the traction/lower the tire slippage, the more that it did so. especially when both rear tires had good traction; potientially causing the whole driveline to bind ... Note that most of the time the front tires were prevented from turning to their limits by tire interference with the frame.
That said when both rear tires had superior traction and one front tire hit a patch of sand, in 2wd. the friction of one front tire trying to turn was, some times, not sufficient to force the rear Detroit to ratchet/release one tire.. resulting in it pushing the front ties side ways instead of turning... put me in the other lane several times; usually in the spring due to sand on the road.

With the soft locker in front I don't remember any excessive steering effort.. it was some years ago now (the ram was installed due to the locked ARB steering effort and its affect on steering box life...it, likely, was unnecessary with the soft locker and only slightly necessary with the 12.50 x 35 inch tires, it did help, noticeably when running the wider much higher traction Boggers though).

With the ARBs that I have had (IF I can remember to turn the front one off (embarrassing))... a slow back and forth with the steering wheel while moving is normally enough to let them release after driving over an obstacle (very similar to getting some old school locking hubs to disengage after a trail run)... occasional drive line binding is , IMO, just going to happen in solid mechanical drive lines.... I don't see it changing until independent electric 4wd becomes common and eliminates a direct mechanical connection between the wheels..

Being lazy, and no longer even trying the semi extreme/very difficult (body damaging) trails any more I just lock the rear at at the trail head on most (not Moab/medium traction or lower) terrain then lock the front in just before the obstacle and unlock it after...I only unlock the rear mid trail (very rarely) if I feel a tire bind and slide, momentarily; as the drive line unwinds (eventually I expect the binding to break a transfer case drive chain).

Enjoy!

Good stuff. Thanks for writing it up.

There is locker technology out there right now from Eaton for the OEM level, and a few guys in New Zealand, that allows for a 'locker' that can be from 0 to 99.99999% locked without binding or wheel movement to engage and disengage. They are using very high hydraulic pressure applied to a piston that compresses a clutch pack in the diff. I even asked Eaton if they would think about releasing it to the aftermarket, they where not interested. They saw it as a very complex traction control system, not just a locking diff. The guys in NZ are building units out of old rare Toyota limited slip differentials that are then heavily modified for the external hydraulics. Auburn tried to do this with magnetic ball ramps but couldn't apply enough force for lock up. They then changed the design.

Generally, when I need the locker to unlock, it is because I need to turn. Having to baby the front locker to get it to unlock is annoying as all get out. This is especially true since I don't have to do any of that in my little jeep because of the front automatic locker. I could just about have the rear locker on a momentary switch with how much I have to use it on the jeep. I can do really difficult trails without having to use the rear locker except for a few feet at a time. The rear locker seems to unlock much more quickly without having to think about it much. I don't have to saw the wheel or anything. Once the rear locker pops out, the front automatic locker more than happy to do it's automatic locker ratchet thing as needed in whatever direction the front wheels are pointing.

I am going to be experimenting with the ability to have left/right rear cutting brakes on the little jeep next. That should even further decrease the use of the rear locker and add some maneuverability at the same time. Dragging the inside rear tire a little really helps the vehicle pivot, especially when using the front locker. Cutting brakes also don't have bind like a locker so there is no worry about getting them to unlock. I would also like to add the ability to drive just the front wheels after that. You can basically pivot the car around the inside rear tire at that point. Unless you want to add rear steering, I think that is the peak of manuverability in a front steer only vehicle.

 

[Buliwyf]

Uphill, medium grip, switch backs, is where I see the benefits of this setup the most. Front autolocker, unlocked rear. Stop and lock the rear if there's a big rock or log in the switchback.

Spool rear, open front, always struggled there. In hindsight, the rear lockers cause understeer more than front autolockers.

 

[nickw]

Those sound like REAR automatic locker issues?

I don't see how a front locker wouldn't cause the same problems, maybe WORSE.

 

[nickw]

I don't know, I don't think locker choice and suspension overlap that much honestly. Suspension is an interesting discussion in itself.

I think the whole suspension vs locker debate was one raging between Mercedes (Gwagen) and Land Rover (Defender/Disco) back in the day. I remember reading something, which delved into their design philosophy. Mercedes taking the stance that less articulation and locked diffs was the way to go while LR took the opposite approach, massive articulation (for a stock rig) with open diffs. They both have their merits in certain circumstances.

 

[MOguy]

I think the whole suspension vs locker debate was one raging between Mercedes (Gwagen) and Land Rover (Defender/Disco) back in the day. I remember reading something, which delved into their design philosophy. Mercedes taking the stance that less articulation and locked diffs was the way to go while LR took the opposite approach, massive articulation (for a stock rig) with open diffs. They both have their merits in certain circumstances.

After years of driving an H1 (very limited articulation) in the Army and years of driving my Jeep ( much more articulation) I can say, without any doubt, that I have never found a situation where I would rather have less articulation.

As far as locker vs, limited slip? Brake modulation works extremely well in an H1, I have front and rear ARBs on the Jeep. Harder off roading the ARB are far better but in milder stuff not have to lock and in lock your diffs (just using a little brake), esp when you need to make a turn is nice. I would still prefer having to lock and unlock my diff for the added traction but I do understand why some may not.

 

[nickw]

After years of driving an H1 (very limited articulation) in the Army and years of driving my Jeep ( much more articulation) I can say, without any doubt, that I have never found a situation where I would rather have less articulation.

As far as locker vs, limited slip? Brake modulation works extremely well in an H1, I have front and rear ARBs on the Jeep. Harder off roading the ARB are far better but in milder stuff not have to lock and in lock your diffs (just using a little brake), esp when you need to make a turn is nice. I would still prefer having to lock and unlock my diff for the added traction but I do understand why some may not.

Hauling and controlling a heavy load probably plays into it. I'm guessing a Jeep isn't going to stand up to up-armoring nor hold a .50 cal like the H1 would. I hear you though, for wheeling, high articulation AND locker is the ultimate. When looking at hard expo-use, Gwagens and LC70 are tops, neither of which have great articulation, but both of which have lockers.

Loved seeing those old Camel Trophy Discovery's back in the 90's (when they had it on TV) rolling and flopping all over the place around corners, seems like those things were always on their sides.

 

[Metcalf]

I don't see how a front locker wouldn't cause the same problems, maybe WORSE.

It doesn't.

I did too, till I actually tried it. Here I am about 7 years later with my flat fender which runs an automatic front locker and rear selectable locker . I ran cross country, hundreds of miles of snow wheeling up north, through two Ultimate Adventures with 4 wheel off-road magazine, and dozens of trips up the harder trails in moab.

A lot of people are stuck in the 'old' way of thinking in my opinion and not really open (ha) to trying different combos.

There are people still thinking about how to do this stuff better....


Here is John Curries thoughts on the matter.


Here is my good ol' flat fender running up Pritchett Canyon in Moab ( try and spot the very intermittent rear locker use )

I always encourage people to think about this stuff. We aren't learning anything new trying the same thing over and over again.

My new build, the #lx45, is seletable/selectable. It hands down it gives up some '3-wheel drive' performance to the old Jeep. I am still testing and evaluating how to make it work better. I built it with hydraulic assist steering to help deal with the steering force issues with the selectable front locker. It helps, but honestly, if it wasn't still full time 4wd, I would seriously consider swapping out the front selectable locker for an automatic locker.

I am adding the ability to control the left/right rear brakes on the old jeep next. Hopefully I will be able to add the ability to drive only the front axle in the near future. I am also going to be replacing the old Dana 30 narrow track front axle with a Roxor front axle. I wouldn't consider anything but an automatic front locker at this point.

 

[Buliwyf]

The army isn't exactly leaving a perfectly flat desert road to run over a small rock pile because it would look cool on a facetube page, either. So the h1 is spec'd as such.

I used to be part of the selectable front, autolocker rear group. Completely backwards, after all of those years. smh.

 

[Metcalf]

After years of driving an H1 (very limited articulation) in the Army and years of driving my Jeep ( much more articulation) I can say, without any doubt, that I have never found a situation where I would rather have less articulation.

As far as locker vs, limited slip? Brake modulation works extremely well in an H1, I have front and rear ARBs on the Jeep. Harder off roading the ARB are far better but in milder stuff not have to lock and in lock your diffs (just using a little brake), esp when you need to make a turn is nice. I would still prefer having to lock and unlock my diff for the added traction but I do understand why some may not.

I'm not saying NO articulation. I am saying MODEST articulation. I have seen TONS of issues, especially on short arm lifted TJs where the suspension has all kinds of bad habits when lifted and running to much shock. The JKs are the same way but a bit less sensitive because of their slightly longer arms. If your vehicle can use ALL of a 10-12" shock that is plenty.

Carrying a tire, especially when talking about the outer fringes of articulation, if it can maintain a controlled predictable feeling for the driver, is not a bad thing. When you add more and more articulation you have to lower the spring rates to keep any kind of preload at full droop. This makes the vehicle feel more and more like a big marshmallow. It will have more torque lean. It will have more body sway at speed.