ARB air lockers???

JPaul

Observer
I would not say the Eaton has the same performance as the ARB. The way they lock is pretty different, in additionto their overall construction. The ARB locks with very minimal turning of the diff (maybe 10 degrees or so) and then stays locked no matter what until air pressure is released. To my knowledge this is regardless of the diff it's in.

The Eaton on the other hand can depend on the diff as to how exactly it operates, whether it's pins that fit into the back of one of the side gears, or a collar setup similar to the ARB, though both styles have the same fundamental actuation mechanism.

The problem with the Eaton is with the actuator mechanism. The electromagnet is used to stop a plate from moving that then causes either ball bearings or pins to slide along ramps cut in the opposing plate that then pushes the locking pins or collar in to mesh and lock with one of the side gears. This then locks the diff so that the axles are forced to turn as one.

Unfortunately, there are a couple shortcomings with this design. The first is that in order for the locker to fully engage you must rotate the axle about 30 plus degrees or more. That can mean rolling forward or backward a foot or more depending on tire size before the axle locks. So if you're stuck already then it's going to take a bit to get the axle locked. Of course the solution to this is to lock the diff before you get stuck, but that isn't always obvious at first.

The second issue ties into the first. When you change directions, such as having to back up to retry an obstacle, the diff will first unlock for about 30 degrees of rotation and then re-lock once it's turned another 30 degrees, so that's about 60 degrees of the diff being unlocked when changing direction. So if you lock the diff, try an obstacle but can't make it up, then when you back up to get a new line or try it again, the diff will unlock for a few feet or so until it re-locks, then when you drive forward again you go through that few feet of an unlocked diff before it locks again. This might put you right back at the very start of the obstacle with an unlocked diff.

Now as long as you are aware of these limitations and take care with driving appropriately the Eaton is just fine to use. But when you don't know about this and think the diff is fully locked when you start an obstacle, then you're going to end up breaking it either catastrophically, or at least drastically shortening its useable life. What happens then is you engage the locker too close to the start of the obstacle (or while in/on it) and it's not fully locked once you hit it, then you may get some wheel spin which turns the diff enough to cause the balls or pins to push the locking pins/collar the rest of the way in, but now everything is moving much faster than you would want it to be when it locks. Then you get a crash lock which at the least will cause the locking pins or collar teeth to start rounding off (if it's the pin type then once they round off enough the locker won't stay locked at all and you'll have to rebuild it), or at worst it will grenade everything.

Same thing can happen if you don't or can't back up far enough when changing direction with the locker engaged.

With an ARB once it is locked it stays locked no matter which direction you go. Yes. You can still crash lock an ARB and cause damage, but it is a fair bit harder to do, and it is only when first engaging the locker, not throughout the session it is locked during. The Eaton can be crash locked far more easily and frequently since it not only has a longer duration of rotation before locking but will also unlock when changing direction, even if it's just rolling backwards a little bit.

On my rear Eaton that grenaded the spider and side gears (GM 8.5" 10 bolt) I noticed that the side gear that the locking pins insert into had surprisingly shallow slots, there really wasn't a lot for the pins to press against. This also resulted in the back of the gear being surprisingly thin which is exactly where the gear ended up losing teeth, in addition to cracking a spider gear in half and busting teeth off the opposite side gear. I also want to point out that this happened while I was tackling a very moderate shelf that several other Hummer H3's got up with very little fanfare and while I was being assisted by very good spotters who acknowledged that I was doing well with following their guidance (which included having very minimal wheel spin). Most likely the gears had already been weakened by the previous owner since he definitely used the truck and put it through its paces. They just happened to end up getting shock loaded one too many times on that ledge and then POP went the weasel. That ledge was a good example of the shortcoming of the Eaton since once I had my front wheels up on it I couldn't back up very far to try to get my rear all the way up it without having to completely back off and try it all over again, so likely the locker kept unlocking and then didn't quite lock when I really needed it to.

The collar type of mechanism is likely stronger but whether you get that vs the pin type is going to depend on your diff. I'm guessing the larger diffs get the collar type and the smaller diffs the pin type, but I'm not sure.

Another difference with the ARB for my diff at least is that instead of just two spider gears, it has three. So not only does it get the stronger collar type locking mechanism (in addition to being always locked once engaged) it also spreads the load out between three spider gears instead of just two.


So all told, while the Eaton is a fine locker, provided you know how it works and thus how to use it properly, and lots of people successfully use them, I definitely would recommend the ARB over the Eaton if you're looking for something a bit stronger, especially if the design Eaton used for your particular diff is the locking pin type vs the collar type, and want a locker that once it is locked, stays locked. Yes, they are more expensive, challenging to install, require additional components to be able to even use them, and add more complexity compared to the Eaton. But personally that is all worth it me after trying the Eaton and having it fail and be a bit of a nuisance to use properly.

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JPaul

Observer
I think a good way to sum up Eaton vs ARB is the Eaton is probably the better choice for someone that doesn't regularly use their lockers, and doesn't often tackle more technical trails, while the ARB is better for someone that gets more technical and is going to be using their lockers more frequently.

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DaveInDenver

Expedition Leader
Ben Brazda talks about how the Eaton/Harrop electric locker cams work and the limitations.

Video from the start:


Jump to the Eaton at 14:17 if you want:
 
Last edited:

MOguy

Explorer
I would not say the Eaton has the same performance as the ARB. The way they lock is pretty different, in additionto their overall construction. The ARB locks with very minimal turning of the diff (maybe 10 degrees or so) and then stays locked no matter what until air pressure is released. To my knowledge this is regardless of the diff it's in.

The Eaton on the other hand can depend on the diff as to how exactly it operates, whether it's pins that fit into the back of one of the side gears, or a collar setup similar to the ARB, though both styles have the same fundamental actuation mechanism.

The problem with the Eaton is with the actuator mechanism. The electromagnet is used to stop a plate from moving that then causes either ball bearings or pins to slide along ramps cut in the opposing plate that then pushes the locking pins or collar in to mesh and lock with one of the side gears. This then locks the diff so that the axles are forced to turn as one.

Unfortunately, there are a couple shortcomings with this design. The first is that in order for the locker to fully engage you must rotate the axle about 30 plus degrees or more. That can mean rolling forward or backward a foot or more depending on tire size before the axle locks. So if you're stuck already then it's going to take a bit to get the axle locked. Of course the solution to this is to lock the diff before you get stuck, but that isn't always obvious at first.

The second issue ties into the first. When you change directions, such as having to back up to retry an obstacle, the diff will first unlock for about 30 degrees of rotation and then re-lock once it's turned another 30 degrees, so that's about 60 degrees of the diff being unlocked when changing direction. So if you lock the diff, try an obstacle but can't make it up, then when you back up to get a new line or try it again, the diff will unlock for a few feet or so until it re-locks, then when you drive forward again you go through that few feet of an unlocked diff before it locks again. This might put you right back at the very start of the obstacle with an unlocked diff.

Now as long as you are aware of these limitations and take care with driving appropriately the Eaton is just fine to use. But when you don't know about this and think the diff is fully locked when you start an obstacle, then you're going to end up breaking it either catastrophically, or at least drastically shortening its useable life. What happens then is you engage the locker too close to the start of the obstacle (or while in/on it) and it's not fully locked once you hit it, then you may get some wheel spin which turns the diff enough to cause the balls or pins to push the locking pins/collar the rest of the way in, but now everything is moving much faster than you would want it to be when it locks. Then you get a crash lock which at the least will cause the locking pins or collar teeth to start rounding off (if it's the pin type then once they round off enough the locker won't stay locked at all and you'll have to rebuild it), or at worst it will grenade everything.

Same thing can happen if you don't or can't back up far enough when changing direction with the locker engaged.

With an ARB once it is locked it stays locked no matter which direction you go. Yes. You can still crash lock an ARB and cause damage, but it is a fair bit harder to do, and it is only when first engaging the locker, not throughout the session it is locked during. The Eaton can be crash locked far more easily and frequently since it not only has a longer duration of rotation before locking but will also unlock when changing direction, even if it's just rolling backwards a little bit.

On my rear Eaton that grenaded the spider and side gears (GM 8.5" 10 bolt) I noticed that the side gear that the locking pins insert into had surprisingly shallow slots, there really wasn't a lot for the pins to press against. This also resulted in the back of the gear being surprisingly thin which is exactly where the gear ended up losing teeth, in addition to cracking a spider gear in half and busting teeth off the opposite side gear. I also want to point out that this happened while I was tackling a very moderate shelf that several other Hummer H3's got up with very little fanfare and while I was being assisted by very good spotters who acknowledged that I was doing well with following their guidance (which included having very minimal wheel spin). Most likely the gears had already been weakened by the previous owner since he definitely used the truck and put it through its paces. They just happened to end up getting shock loaded one too many times on that ledge and then POP went the weasel. That ledge was a good example of the shortcoming of the Eaton since once I had my front wheels up on it I couldn't back up very far to try to get my rear all the way up it without having to completely back off and try it all over again, so likely the locker kept unlocking and then didn't quite lock when I really needed it to.

The collar type of mechanism is likely stronger but whether you get that vs the pin type is going to depend on your diff. I'm guessing the larger diffs get the collar type and the smaller diffs the pin type, but I'm not sure.

Another difference with the ARB for my diff at least is that instead of just two spider gears, it has three. So not only does it get the stronger collar type locking mechanism (in addition to being always locked once engaged) it also spreads the load out between three spider gears instead of just two.


So all told, while the Eaton is a fine locker, provided you know how it works and thus how to use it properly, and lots of people successfully use them, I definitely would recommend the ARB over the Eaton if you're looking for something a bit stronger, especially if the design Eaton used for your particular diff is the locking pin type vs the collar type, and want a locker that once it is locked, stays locked. Yes, they are more expensive, challenging to install, require additional components to be able to even use them, and add more complexity compared to the Eaton. But personally that is all worth it me after trying the Eaton and having it fail and be a bit of a nuisance to use properly.

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I did not know all this.

I will change my answer.

Eatons suck, ARBs kick ass!
 

Metcalf

Expedition Leader
Personally, I like avoiding high pressure rotary air pressure seals....that rules out the ARB and Yukon Zip locker for me unless I don't have any other choice. While an ARB or similar unit carefully and thoughtfully installed can provide years of faithful service, it can also be a nightmare, especially if you have to remove the carrier in the field. This can and does happen when you really don't want it to. I have had to deal with a lot of leaky half broken ARB units on the trail.

When available, I really like the OX locker system. The version with the small air cylinder built into the diff cover seems to give all the bonuses of an ARB without the downsides of high speed high pressure rotary seals. You can pull the cover or carrier without having to worry about messing up the rotary seals, the copper line junction, etc. I've been running one in my flatty for almost a decade now with no issues. The air fittings are all common 1/4" nylon air brake stuff available at any local parts house if you have issues. You can also over-ride the air cylinder with a small screw in bolt to lock the diff without an air pressure source.

My favorite locker combo so far to date for what I do overall has been an automatic locker in front and a selectable rear locker. That seems to have the least drama and best all around performance for me. Vehicle maneuverability in '3wd' is the best of all the different combos I have tried, including selectable/selectable ( I own both ). With the front automatic locker my front end just goes where I point it. The vehicle doesn't push through turns with the rear diff open. I can honestly do a LOT of pretty difficult trails with only momentary use of the rear locker.
 

Metcalf

Expedition Leader
Also, just a note on the Eaton E-Lockers ( and the new Auburn unit ).

In the Dana 60-70-80 sizes they now offer a completely new locking mechanism that eliminates the 'ramp' and 'pin' function. The new design is much much stronger. It doesn't potentially lock-unlock-lock when changing directions. It locks up MUCH quicker with minimal rotational movement.

I would suspect we see this trickle down into smaller sizes soon.
 

JPaul

Observer
Ditching the ramp mechanism would be great, aside from using pins on some of the lockers that is the only real issue I have with Eatons.

And yeah, it's not that Eatons suck, they just have some very real shortcomings. As mentioned though, ARB has some weaknesses as well, but I feel the tradeoff is better. Eatons are great for people that want a simple locker that doesn't require extra expense to operate and is relatively maintenance free provided you use it properly. Probably most overlanders can go with an Eaton and have no issues. Once you're in the rocks though they just don't cut it in my opinion.

I looked at OX since it's fully mechanical and no internal air seals to wear out or air lines to break (unless you use the air actuator) and if your choice of actuator (cable, electric solenoid, air solenoid) breaks then you can still manually lock it with their little doohickey.

However, when I looked into them I kept seeing a disproportionate amount of negative feedback about them, so that scared me away from trying them. Maybe things have changed, but I wasn't willing to drop a couple grand for them to find out for myself.

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Metcalf

Expedition Leader
However, when I looked into them I kept seeing a disproportionate amount of negative feedback about them, so that scared me away from trying them. Maybe things have changed, but I wasn't willing to drop a couple grand for them to find out for myself.

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I've been running an OX locker for almost a decade. Zero issues.
 

WSS

Rock Stacker
My last Jeep ('72 CJ5) had ARB's front and back. My TJ however has a Yukon zip on the NEW Currie rockjock D44. Currie actually recommended it for a few reasons. A) it was cheaper by a 100 or so and B) it has a better (less questions asked) warranty than ARB. Now, I have never had need of warranty on a ARB so it may be a moot point. But I did notice lots of guys running Ultra4 cars and KOH rigs running Yukon lockers. Food for thought.....
 

01tundra

Explorer
Ran them for many years in multiple front and rear axles and never had a single issue.

Destroyed several ring & pinion sets, alloy axles, etc and never had an ARB failure.



 
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