The back story on this is that my long term plans were to retrofit the stock elocker (with the 4.30 gear ratio?) on the rear, and maybe do something with the front diff later on. Now my oil pan RTV gasket is failing, and fixing that gasket is now the next big project. Replacing that gasket requires pulling the front diff out, and so while its out and easily accessible I might as well do something with the front diff.

I've already done some research. I could either do a limited slip differential by someone Truetrac, or a l̶u̶n̶c̶h̶b̶o̶x̶ air locker from someone like ARB. Both have their strengths and weaknesses.

The limited slip differential would be far less expensive to do, it doesn't require miles of vaccuum tubing or additional wiring, and it will help get traction in inclement weather* (I'm coming back to this). It is also a bit simpler to maintain that an external system. There are a few cons, first there's no way to control it its totally automatic and so you cant turn it off like a l̶u̶n̶c̶h̶b̶o̶x̶ air locker , the 2nd downside is that it could theoretically lock the wheels as you turn and make it hard to steer. Also I mentioned that its better in inclement weather like snow, and it is but you have to drive carefully otherwise the wheels will both spin out (sort of like how people would weld diffs to do drifting).

Now onto locking diffs. The upsides is increased capability, ability to control when its locked, sounds cool to say twin lockers, and more predictability. Downsides are cost, and if you are rough on a IFS locker you will break something. You also have to have space to fit a compressor under the hood, on my 3rz non ABS 4runner that is easy.

Anyone have anything else to add?

Edit: I accidently used the term lunchbox locker in this post. I thought this was a term for any lockable diff on an ifs vehicle, whoops. Further research into this term got even more confusing, so I'm not using it and will put in quotes the correct term. What I mean to say was air locker.

Both of my T4Rs have front & rear TrueTracs.

Steering load is not significantly increased when in 4WD.

Very much *NOT* something I'm familiar with beyond idle entertainment (like the youtube channel 4wd 24-7, they talked about this) ~ but what about the lock right type lockers? Lock Right Locker - PowerTrax

FYI: "Lunchbox lockers" are a style of automated locker like what Brian posted above, that CANT be manually controlled, and as far as I know something ARB never made - they only make air lockers which are top of the line and have bills to match. Another example of a lunchbox would be a Spartan locker. Very different in almost every way, however lots of people like lunchboxes and plenty on here run them. Arguably as many as air lockers I'd say, simply because of the cost of adding one

One additional nice thing about getting an ARB is you now have a compressor to fill your tires (unless you get the super small compressor). Also for my front locker I probably used like 2-3’ of tubing which really wasn’t that bad.

What's your use case that you need/want a front locker? What's your budget?

ARB is by far the strongest.
TrueTrac the second strongest.
Lunchbox by far the weakest.

ARB is a selectable locker. Meaning you can turn it on or off. When off the front diff acts just like a normal open diff. When on it's fully locked and each wheel get's 50% power regardless of whether that wheel is in the air, mud, sand, snow.

TrueTrac is an LSD. They act similar to a real locker but they are far from it. In most cases when you have some traction to both wheels they do just fine. Once you lift a wheel they act just like a normal open diff. That lifted wheel get's almost all the power. Not what you want if rock crawling. No one I crawl with uses them for that reason.

Lucnhbox lockers are non-selectable drop in units that use the stock carrier. They unlock when turning using a spring loaded locking pin and centrifugal force. Some people love them because they are cheap and can be installed without any knowledge of how to properly set up a diff. The downside is they are weak and they make a noise when locking and unlocking.

Harrop also makes a selectable front locker that's electric for the 7.5" front diff. It works just like the ARB but uses magnets to move the locking pin instead of air.

I didn't realize exactly what a lunchbox locker was, but further searching revealed enough for me to realize I don't want one. When I was looking for my third gen I drove one which likely had a lunchbox on it, it would bind around corners and it sounded terrible.

Limited slip or airlocker is what I meant to say.

Do limited slip differentials in the front have the same downsides as they do in the rear?

If I did fit an air locker in the front it wouldn't make much sense not to fit one in the rear as well since a majority of the hardware would already be in place. If you consider that the total is 5k (RD90 front RD132 rear, plus all the kit needed), I wouldn't do this all at once but that is till a large price.

If I eventually put an air locker in the back would it at least save me the trouble of changing the rear gear ratio like I would if I went with the stock E-locker?

Does anyone besides ARB make air lockers for our 4runners?

Also I think the truetrac LSD for our 4runners was discontinued

Front TT: 911A342 or 911A644, they may be interchangeable
Rear TT: 913A610

Looks like they are still around

The axle shaft diameter for the 911A342 that does show up on their website is 1.12 inches while the 911A644 was 1.3 inch axle shaft diameter. Does that matter?

I thought the Harrop (I think now Eaton) lockers got great reviews. Someone I know and respect in the industry said he'd go with an Eaton locker any day of the week over an ARB. This is a guy who knows his shit, owns a Toyota shop and has lots of experience wheeling. I know you have a lot of experience wheeling as well so what's your opinion on the Eaton lockers.

I've only wheeled with one guy that uses his Harrop hard. After about 8 trips the electromagnet failed. That was replaced under warranty. After another 6 trips it failed again. He now runs an ARB.

I know Harrops are super popular in Australia so I don't think there's a major issue with them. He might have just been really unlucky.

ARB's also have there own set of issues. Solenoids can fail. Pressure regs fail. Lines fail. Gear oil can get into the lines and so on. No system is gonna be 100% bomber.

The reason I run ARB is it's hands down the strongest locker on the market for our trucks. I've broken and continue to break lots of stuff crawling. One thing I don't worry about is my lockers.

Thanks for the info. I was thinking if I went with a front locker I'd go with a Harrop but now you got me thinking.

Anything abused or just used will break or wear out over time.

I saw that Eaton makes E-lockers for our 4runners front diff(Part number 14218-1), it cost more than an ARB air locker at nearly 1300. But you dont need an expensive air compressor for an elocker. It probably pairs better if you already have the stock e-locker, and an elocker seem more durable to me.

Best to ask an expert like Chase at ECGS

Harrop (Eaton) E-lockers have a problem with unlocking when you change drive direction.
Harrop Eaton E-locker Disengagement Examples | Watch before you buy - YouTube