Front ARB Air Locker DIY & Install Thread

When I began to do my research to find helpful hints with front diff work and ARB installs on 8” IFS clamshells I was pretty disappointed to find very little information. These diffs have been in use in Tacomas since ’05 so it’s time everyone stop being so afraid and start digging in. Hopefully this thread will be a resource and encouragement for those interested in doing this themselves.

I have a done a fair amount of gear, diff, axle, and drivetrain work in my day but never with the IFS clamshells. This was an opportunity to rectify that. There definitely is a learning curve when you’re used to solid axles and drop out 3rd members and the clamshell diffs are somewhat frustrating to work with and setup. But the frustration is mostly in the extra time and effort it takes to make a change and then check and measure specs. Otherwise, it’s just like any other diff. Also, it sucks a bit having to rip the entire thing out of the truck.

There are also some items with the ARB air system in this diff that are more challenging than normal. Had I seen a decent description of some of the details it would’ve saved me some headache as some of the information in the ARB install manual I determined you don’t really want to follow, especially with the newest version bulkhead.

I know some on this board have done this work themselves and I encourage them to drop any helpful tips they discovered along the way. Pictures will help too.

The truck is a 2016 Off Road M/T but this is the same diff in all the 4x4’s since 2005. I think the main change from 2nd gen to 3rd gen is the 2016+ diffs have the oil temperature sensor. This came in handy after the install.

This is the only bit of good detailed information I found on the 8” clamshell. He covers a gear and ARB install. https://www.fjcruiserforums.com/thr...-4-56-gears-and-arb-install-with-pics.527641/

Parts used:
ARB Air Locker RD111 (for 3.91 and numerically higher gears)
Nitro Gear Mini Install Kit (reused my old bearings)
RTV
Upgraded -006 o-rings for the bulkhead – McMaster p/n 8297T116 - Contact me if you'd like a few
Extra -136 quad rings for the seal housing – McMaster p/n 6540K237 - Contact me if you need extras

Tools Needed:
Typical wrenches, sockets, prybars, screw drivers, hammers, punches, impact gun, etc.
Dial indicator with right angle attachment or test indicator and stand
Beam or dial style in*lbf torque wrench
7/16 drill bit and ¼” NPT tap
Brass punch
35mm and 30mm sockets
Torque wrench
Bearing puller - I use the clamshell bearing puller and it is worth its weight in gold. Super easy, super fast, and zero damage. I will never not have one of these.
Press - I still don’t have one in my garage, but got creative.
Jack and jack stands


Before you start get the truck up safely on jack stands and remove the front tires and skid plates.

Diff Removal

1) Remove the front axle hub nut. Get a screwdriver behind the hub dust cover and remove it. Under that you remove the cotter pin and blue lock cap. Next zip off the front axle hub nut with a 35mm socket. It’s torqued to 173 ft*lbf but the 'ol harbor freight earthquake didn’t care. Before moving on I hit the CV end with a dead blow to make sure it was broken free from the hub.


2) Remove the two bolts at the bottom of the steering knuckle that attach the lower ball joint. These are torqued to 118 ft*lbf and when reinstalled I used red Loctite.



3) From here you’re good and can swing the knuckle out of the way to remove the outer end of the CV from the hub. Pro Tip: When working on the driver side turn the steering wheel to the right a little over one revolution and work from the rear of the knuckle to remove the CV. This helps get the angle and clearance you need as you slide the CV out of the hub. Do the same on the passenger side but with the wheel turned to the left. I used small jack stands to kind of support the hub and end of the CV as I was working.


4) Hammer the CV’s out of the diff using the stock notches on the inner CV joint. I found a prybar or large screwdriver didn’t do the trick as the handle absorbed too much energy to punch the c-clip into the splines. A solid, flat punch did the trick with ease and the CV’s almost jumped out on their own when they saw that coming.


5) Disconnect wiring harness. Easiest method here is unplug the ADD actuator and temp sensor. Remove the harness to the temp sensor from the axle tube by pulling it straight out. On top of the tube on the passenger side is a bracket that holds the harnessing. There’s a 12mm up on top and just unbolt that and leave all the wiring right there in the truck tied up out of the way.

6) Disconnect breather hoses. There are soft lines from the ADD and top of the diff to solid lines on a bracket that then transition back to soft lines up near the frame rail. I think the easiest way here is unhook the soft line at the diff breather and ADD actuator and then get on top for another 12mm on the bracket and leave all that hanging up in the truck.


7) Disconnect the front drive shaft from the front diff.

8) Finally, unbolt the 2 front diff mounts and the rear mount that uses a 12mm allen and remove the diff. I found the trick was to use the jack, rotate the diff forward and begin to lower it while swinging the passenger side tube towards the rear of the truck and watching the pinion so it clears everything. It’s an odd little path it takes, but it will come out easier than it goes back in. Leaving the front arm mounts on the diff gives you something to hang on to and provides some leverage.


Diff Teardown

1) Unbolt ADD actuator. Makes access to the next bolts easier.

2) Unbolt the passenger side diff tube. These are torx heads.

3) Pop out the differential side gear inter shaft sub-assembly. This is what the ADD clutch engages to tie the passenger side axle to the passenger side gear in the diff. This comes out super easy with two opposing prybars. I know some people get fancy with a slide hammer or snake a long screwdriver all the way through the diff but that’s nonsense compared to the 2 seconds to pop it out with prybars.


4) At this point it’s a good time to get a couple measurements of the stock setup: backlash and total preload. This gives you an idea if there are any problems to fix and provides a benchmark preload for final assembly. Also, doing this now will let you know if you have the tools you need to go forward.


5) Time to split the clamshell. Remove the 10 bolts, they’re torqued to 37 ft*lbf, and knock off the shallow half of the clamshell. It’s probably on there good but there are tabs to help you hammer it apart with a punch and it’s likely going to be tight on the 2 dowel pins.


6) Remove the carrier and ring gear. I found this best to do by kind of rolling the diff upright and dumping the carrier out a bit. I also put it back in with this method so I wasn’t dropping the ring gear onto the pinion gear.



7) With the carrier out remove the 10 ring gear bolts and with a punch and hammer knock off the ring gear. Make sure it falls onto something soft like a couple blocks of wood or a pile of towels.



8) If reusing bearings, pull off the carrier bearings with a puller and be sure to keep track of which goes where so they stay matched up with their race in the clamshell housing.


9) Before moving on it’s a good idea to get a preload measurement on just the pinion with the carrier removed. This way you have your baseline pinion preload so whatever you measure above this in total when assembled is carrier bearing preload. You’ll need to use your in*lbf beam or dial style torque wrench adapted to a 30mm socket. My ¼” to ½” adapter setup still lives with my other wrench in another location, so I got creative and made it work with a flat head screwdriver socket.


10) Tear down is complete. From here on out it’s reassembly.


Install Locker

1) Install ring gear. Check the surface of the ring gear and locker for any high spots or burrs and file or stone them off. Next clean the threads in the ring gear and all the ring gear bolts so they are clean and dry. Heat the ring gear, as it’s a tight fit, and make sure it’s aligned with bolt holes before beating it on with a dead blow. Install ring gear bolts with red Loctite and torque to 71 ft*lbf.

2) Using a press, press the carrier bearings back onto the locker. I used an old gear from a Toyota transfer case and ground a bevel on the ID which made it a match to the inner race of the carrier bearing. I did this with a work bench turned sideways for the press frame and my stock bottle jack.


3) Now it’s time to start making adjustments and test fitting until the gears and bearings are back in spec with the new locker. All the shims you need to change live under the carrier bearing races in the clamshell so every time an adjustment is made one or both races will get removed and reinstalled. I just do this with a hammer and punches. As long as you’re careful, don’t hit anything too important, and keep the races square you’re good to go. You can take all the measurements like the ARB install instructions suggest or you can jump right into a test fit. Typically, the adjustments that need to be made should not be large as the ARB stuff (and most quality lockers) should drop in and be close to the factory setup.


4) I suggest leaving the deep carrier bearing race and shim plate as is to start and just making the first adjustment at the bearing in the shallow half of the clamshell until you figure out ballpark preload. The first time you take out the shallow half race also carefully knock out the side bearing retainer deflector and set it aside. I wouldn’t go into the deep half until I knew I needed to change backlash or if I found that I had zero backlash and the pinion was contacting the ring gear on these trial assemblies. The shallow half race has to come out no matter what as the seal housing for the ARB lives behind this race. If I was doing this job again, I would measure the thickness of the seal housing and create a shim stack that matches the thickness or a couple thousandths less. It was 0.138” on my examples. I would use this stack to represent the seal housing until I was close to final assembly. This would keep all the wear and tear off the seal housing and copper line as it comes in and out during setup.

5) Once you start doing test fits you just assemble the clamshell fully together each time and measure total bearing preload and backlash. The carrier bearing preload comes from measuring the total breakaway torque and subtracting what you know is from the pinion. Remember taking that measurement? The spec for the backlash is 0.004”-0.008” and the spec for the carrier bearing preload is 2-8 in*lbf. I think 2 in*lbf is a little light for carrier bearing preload and I shot for the higher end of the range. You can also measure preload by measuring the gap in the clamshells before they’re bolted together but there are 2 issues with this. One, the dowel pins make this difficult as they offer the most resistance and sanding them until they were a slip fit seemed unnecessary and, two, nowhere in the factory service manual is there a spec for how much end gap would give spec’d preload. The factory service manual works all off total preload measurements. In the FJ install I referenced in the beginning he did find that an 0.008” gap provided about 6 in*lbf of carrier bearing preload. Also check on your first assembly or two that when the diff is assembled there’s no free float in the carrier left to right indicating a gap is present and more shims must be added.

6) All said and done I ended up with 0.100” of total shim with 0.076” in the deep half of the clamshell and 0.024” under the seal housing in the shallow half of the clamshell. This gave me 22-24 in*lbf of total preload and 0.007” backlash. This matched with the FJ install referenced where he ended up with 0.100” as well but split differently between the two halves of the clamshell to end up with similar backlash. As a rule of thumb for all diffs, a shim change nets a backlash change of about 0.7x of the size of the shim change. I found with this diff the backlash change is a little greater and maybe around 0.8x-0.9x of the size of the shim change. My carrier bearing preload is a little high according to spec and I’m good with that. I go through a lot of shims, but eventually get it just right.


7) Once everything is where it needs to be I suggest running a pattern and verifying everything looks good. When doing a locker install like this if the original gears were set up properly there should be no problems as nothing done should necessitate any need to adjust pinion depth. This is just confirmation that everything is good to go.


8) At this point you are ready for moving on to the seal housing work before the final install.


Seal Housing and Bulkhead Install

This is where the install gets critical and where I had the most frustrating issues. If you do this right you can enjoy a long lasting, leak free air locker that locks on command and brings you great joy. However, if you do this wrong you’re in for a world of pain with leaking air lines, a pressurized diff, oil misting, and unnecessary diff removals and tear downs to troubleshoot problems. Pay attention here, do it right, and all will be well. Yes, the e-lockers are easier in this aspect, but they lack the actuating power, do not lock and unlock like an air system, and the mechanical design is not nearly as simple, fool-proof, or robust.


I had the newest style ARB bulkhead fitting. In the end I did it how it made sense and didn’t worry with the instructions in the manual and it worked out well.


1) First thing to do is drill and tap the hole for the bulkhead. Do locate this spot by following the instruction in the ARB install manual. Work your way up to a 7/16” hole and tap with ¼” NPT tap. While doing this use the bulkhead fitting to determine how far to tap. I went until the bulkhead fitting only had a thread or two showing above the hole. If you go too far the tapered bulkhead won’t be able to tighten up and seal.


2) At this point, the best thing to do is throw the ARB install manual in the garbage. From here on out the instructions are incomplete, contradictory, and improper. I feel like it hasn’t been properly updated for the new bulkhead nor is it thorough for the 8” IFS diff.

3) It’s time to adjust the copper line to shape, trim it, and install the seal housing in the shallow clamshell half. Remember when installing the seal housing that all the shims must go on the side with the copper line connection and NEVER between the seal housing and the bearing race. In the install manual you are instructed to trim the copper line so it sticks out of your tapped hole by 8mm. Do not do this. This is way too long and if you do this, by the time you install the center compression nut to seal the copper line in the bulkhead you will have pushed 8mm worth of copper line back into the diff. In some diffs this is no big deal as there is tons of room and 8mm means nothing to a long run of copper line living in lots of free space. In this diff there is very little wiggle room and if you shove that much copper line back in it’s hard to find a place for it to go as things are in the way and the run is so short it doesn’t bend easily or cleanly. I routed my line so that in ran along the seal housing clearing the wall of the diff housing and not protruding at all into the center where the inter shaft sub-assembly lives. You also want to keep the line tight against the seal housing as it routes around and we’ll cover why later. I trimmed my line so that once installed it ran through the tapped hole and sat flush or slightly protruded from the outside surface of the diff housing. This is a far cry from the 8mm the install manual suggests. Warning, this makes it more difficult to install the -006 o-rings and small spacer as it’s recessed well into the bulkhead fitting but it’s very doable and will keep your line as routed when you get to sealing it all up with the center compression nut. Just pay attention here to where the end of the copper line really will want to be once all the parts are assembled in the bulkhead. As you install this seal housing, rotating it with a punch and hammer may help you snake it all in there and get it aligned with the tapped hole.


4) If the copper line looks good and is sitting in the tapped hole as desired, install the bearing race against the seal housing. At this point test that the end of the copper line isn’t deformed and fits easily through the small spacer you’ll use later. If it doesn’t fit over easily now is the time to massage and file and sand the end of the copper line so it does. Also, clean out the seal housing and install both quad rings (x-rings) and be 100% sure they are not twisted. I use plenty of grease on the quad rings.

5) Install the bulkhead body. I used small punches to center up the copper line, applied Teflon tape to the threads of the bulkhead body, and threaded the bulkhead body in over the copper line.


6) Complete installation of the bulkhead fitting to the copper line. You will work inside the bulkhead and get one -006 o-ring over the copper line, followed by the small spacer, and then install another -006 o-ring. I upgraded these -006 o-rings. I believe the ones that come with the bulkhead kit are hard 90A Buna-N o-rings. I just upgraded to hard 90A Viton o-rings. They were a little pricey. Finish up the bulkhead by installing the center compression nut into the bulkhead body. This should contact the copper line and squeeze the two o-rings as it bottoms out, sealing the outside of the copper line to the inside of the bulkhead body. This is where you don’t want to push much line back into the diff, but you do need the end of the copper line to contact the center of the compression nut. If you get through this successfully, you’re home free. I used plenty grease to get the o-rings and spacers installed with a small pin punch and a small tapered punch. Worked easy.


7) Assemble the whole diff again and confirm backlash and total preload. Pro Tip: When you assembly the shallow clamshell half onto the locker be extremely careful that the quad rings do not get pinched going over the carrier. This is very easy to have happen. Just slowly apply and release pressure on the quad ring so it flows into the gland. I also use the smooth back side of a curved pick to help the quad rings get in the gland and not get pinched. If you pinch these, you will eventually leak if not immediately. This is very important and always be careful when getting these quad rings over the locker.

8) Moment of truth. Install an air line and pressure test the air locker. I used the ARB compressor and air solenoid already installed in my truck and attached the 6mm air line with the compression nut and ferrule to the bulkhead body. There are two ferrules that come with the air locker so I used one for my pressure testing and a new one for final assembly in the truck. I also already have a pressure gauge installed on my compressor so used that to do a leak down check, but if it leaks it will turn the compressor on anyway. Sure enough, I had a leak at the soldered connection of the copper line to the seal housing. I was able to get a replacement from ECGS who had 2 in stock. Ordered on Monday, arrived Tuesday morning. ECGS is the best gear shop there is. This gave me a second chance to properly install my seal housing and it worked out much better with the lessons previously learned.


9) When all is good and everything is within spec, pull off the shallow clamshell half one last time, apply RTV to the clamshell, reassemble, and torque all the bolts to 37 ft*lbf.

10) This is the last important step to guarantee trouble free air locking and proper 4wd shifting. Nothing about this is covered in the ARB install manual and I’ve never heard it mentioned. It’s important to recognize that where the copper air line lives is right at the edge of where the ADD clutch sleeve translates to when the truck shifts to 4wd. If you don’t have adequate room or leave out the retainer deflector the clutch sleeve could hit the copper line and rub against it as it spins or the line could keep the actuator from properly engaging the side gear inter shaft. The retainer deflector that was removed earlier has two tabs that go around the breather hole in the diff. This cannot be installed back in the diff this way as the ARB seal housing takes up the space where the ears used to be. I decided to reinstall retainer deflector as a barrier between the ADD clutch sleeve and the copper air line. This is why you want the air line tight against the seal housing as it gives room to tap the retainer deflector back into place. I snipped the ears off the retainer deflector, pushed the copper line tight to the seal housing and installed the retainer deflector until it touched the copper line where it lifts up to get into the bulkhead. The retainer deflector will now be what the ADD clutch sleeve contacts if it floats far enough in the engaged state. Once this was done I felt good that my copper air line was protected long term.



11) Reinstall the side gear inter shaft sub-assembly and check that the copper line is clear of it and the ADD clutch sleeve when engaged over the inter shaft.




Final Notes

From here it’s just a matter of reattaching and rtv’ing the differential tube to the clamshell, the ADD actuator to the housing, replacing the axle seals, and reinstalling the diff back in the truck. The diff snakes in the same way it came out and the CV shafts hammer in the same way. Once it’s all buttoned up and torqued you’re done!

I attached my air line with the banjo fitting to get it exiting at a right angle. You can see I dropped the diff during install one time and bent the differential oil temperature sensor. Still works just fine.



I broke my bearings back in by driving around in 2wd with the diff locked. When you do this you want to engage the locker while you’re stopped. During normal 2wd operation the driver side tire is spinning the left side gear in the diff. Since the pass side of the diff is disconnected, the friction in the open differential itself is much less than the friction required to spin the ring gear, pinion gear, drive shaft, and transfer case chain. Because of the friction levels and the characteristics of an open diff, the ring gear and front drive shaft don't spin and just the gears in the differential do. This causes the right side gear to rotate at a speed equal to the left side gear but in the opposite direction while the carrier itself is stationary. If you tried to lock the diff in this state you have a static carrier and spinning side gear and since these are the items locked together there will be nothing but grind and likely a trashed clutch gear.

If you wanted to shift the front locker at speed you need to first shift into 4wd which will engage everything and get a speed match in the differential. From there you can engage the locker. Be ready as when it engages there may be a slight tug on the steering wheel. Once it’s engaged you can shift back to 2wd leaving the front diff locked. The pass side ADD will disengage but the driver side tire will continue to spin the carrier and front drive shaft since it is still directly linked through the locked diff.

I found that my front differential temperature when open in 2wd would settle at about 30 degF above ambient on the highway. With the front diff locked in 2wd the temperature would settle at about 80 degF above ambient since there was heat now coming from the carrier bearings, ring and pinion mesh, pinion bearings, and extra load from the free spinning inertia of the front drive system whereas unlocked the only friction comes from the side and spider gears spinning inside the differential case.



I basically just wanted to get heat cycles on everything without operating it for an ended period of time. The only gears that will get broken in are the new gears in the open differential of the the ARB. I will change the oil after getting some miles on it and expect some metallic particles from these gears. After that, good to go.

 

*Reserved* for diagrams and such.

Factory Service Manual Illustrations with Torque Specs


Inside the ARB Air Locker


ARB Exploded View

 

Thanks, this is awesome and probaly the most informative post I've ever seen. I'll be up all night for obvious reasons and reading through this.

 

Tremendous post, and although it is too much of a job for me to take on, it really helps to appreciate what goes into this. Thanks!

 

Subscribe for future reference.

thanks for sharing

 

I raise my hand sheepishly and say I didn't have the guts or place to do mine, maybe the skills over 2-3 weeks, most of the tools.

I bow down to an excellent thread!! Very good.

 

Excellent!!!

 

Very nice write up! I was considering the e-locker until I bought a series 80 land cruiser. Still may pick up a front locker one day once I finish my land cruiser build.

 

@EatSleepTacos

 

Wow, while it’s unlikely I’ll ever lock my front, amazing contribution. That’s a lot of effort to put that together. Better instruction and pictures than I’ve ever seen in repair manuals and service manuals I’ve paid for.

 

Great write up! I can't see myself doing an ARB front locker just yet but it was seriously a much needed read compared to the "tire question", "new pro owner lift question", and "need help on finding vibration" threads that pollute TW. Beers are on us OP.

 

If I didn't know this was an ARB and someone just showed me pics, I'd never believe this was a robust setup haha. I always just assumed I would possess the skills need to add a front locker but idk if I could. Just reaching in with that test indicator would have me second guessing myself haha.


Some supplemental info for other newbs like me.


https://youtu.be/dAqAqODmcj4

 

I just made a post for wiring up a locker switch that will only allow you to engage when you are in 4 Low, if that may be of interest.
https://www.tacomaworld.com/threads...rket-front-rear-lockers.758203/#post-27022700

 

Awesome write up! I have an air leak which I believe is the bonded seal. Can I split the clamshell and dump out the carrier and replace the seal. Then put it back together and be fine? I have a crush sleeve and I’m not sure if cracking it open causes more problems with preload and all that jazz. I bought the locker secondhand and had a shop put it together last week for me. They couldn’t find, lost or maybe find some of the bulk head fittings so I pulled it tonight and put it in and there’s a leak. I have it laying on a rubber mat so the other side is sealed and filled up around the copper line, seal and fitting flush to the top with gear oil. In the picture below you can see air is coming up through the one passageway into the diff. Doesn’t look like anything else is leaking in that area.

 

I wouldn't jump right to that conclusion. The leak might still be the seal housing or seal housing o-rings. So check this first. Note the twisting or pinching of the quad rings in the seal housing on reassembly of the clamshell half. I still have extras of these.

If it's all setup properly you can crack it open and just reassemble as it is after repairing any leak. You won't touch the pinion so no crush washer is needed. Same for the backlash and carrier bearing preload, you won't be touching any of that either.

Follow through all the info in the write up and it'll walk you through splitting the clamshell and dropping out carrier. To get to the bonded seal you will have to pull the ring gear off the carrier and split the carrier in half.