Front TRE Air Locker Install - Follow Along!

[Nenw]

I'm doing it. I didn't think I would but I'm biting the bullet and going to install a front locker.

In the past there were 2 options that I knew of. 1. get a Lokka Lunch Box locker or 2. find the 8" diff from a gen one Montero and go ARB.

Well, there is a third option now. TRE 4x4 is offering a 7.25" Air locker, pretty much an ARB knockoff from what I have read. And if you look at their site, well, it's everything is a straight-up rip-off of ARB. If ARB had a locker for me, I might care, but beggars can't be choosers so here I am.

I do not know of anyone who has installed one of these yet and well, I've called like 5 or so shops and no one wants to get into it either because they are wusses and will only play with Toyota or Jeep. Or they only want to install things you bought through them. The one shop that sounded okay to do it, mentioned that they charge like $800 to do a bench install for a Toyota. Not worth it for me on top of the other $1000 in parts.

That is okay though because I like learning things.... especially hard things. So, I decided to take this on, to get some tools and develop a new skill set.

I do not intend to walk through how to install a diff. I do not know how to do this. I am going to learn in the process. There are a ton of resources out there to learn from. This will just be my experience, preparations, challenges, and a place to call on some of you all for some backup.

I am using a donor pumpkin provided by Josh Q and his super van. He just recently swapped to an 8" front diff.

The Air Locker comes care of @13mclean. I found it he bought it. I was going to buy another but Marco at Luso Overland mentioned we should check fit before buying a second. Solid suggestion since no one has done this install yet. @13mclean had other things going on so I am doing the initial legwork on this. Maybe if I get this good, I can trade him the labor to do his in return to build me a rear bumper

TRE AIR LOCKER:

• TR311 - 7.25", 25 Spline for A/T
• TR309 - 7.25", 28 Spline for M/T
• Viton 039 75A O-Ring - Note, not necessary but the O-ring is a critical component. TRE may have cut costs on this. You can get cheaper but this one is Military Spec. I would rather not have to tear into the diff a second time because a shitty consumable failed.

Diff Parts List:

• MB092348 - Side Bearing (case) - QTY 2
• MB290013 - Side Seal (case) - QTY 2
• MB430694 - Center Isolator Bushing - QTY 1
• MB160578 - Rear Seal - QTY 1
• MB290962 - Rear Bearing outer - QTY 1
• MB290960 - Rear Bearing inner - QTY 2 - Note that only one is necessary for the install. The second is to use for setting pinion preload.
• MB160387 - Passenger Side Clip (Diff Side) - QTY 1
• MA143517 - Prop Shaft Nut - QTY 1
• MB185351 - Shim Set, Fr Diff Drive Pinion, Fr; Shim Set, Rr Diff Drive Pinion, Rr (Pinion Height) - QTY 1
• MB569391 - Shim Set, Fr Diff Drive Pinion (Pinion Preload) - QTY 1
• MB185519 or ARB SHK-008* - Spacer Set,Fr Diff; Spacer Set,Rr Diff - QTY 2
• MB518676 - Side Bushings - QTY 2 - Not required but since you are in there.
• MB160946 - Dust Seal Housing - Axle Tube - QTY 1
• MB001294 - Drain Plug Crush Washer - QTY 1

*Note about the ARB shims. No one has these in stock and they will show very long lead times. Call your local off-road shop and have them place an order direct with ARB. Summit was showing a 2 month lead time, 2 other online retailers had canceled on me. I called ARB and they had 50pc in stock. They had me contact my local shop. I had them within a week.

The "While I am at it" List

Upright:

• MB160670 - Needle Bearings - QTY 2
• MB160671 - Spacer - QTY 2
• MB160850 - Inner Seal - QTY 2

CV REBUILD

• MB393911 - (A/T) Driver Side Clip (Diff Side for axle) - QTY 1
• MB393884 - (M/T) Driver Side Clip (Diff Side for axle) - QTY 1
• MB160387 - (A/T) Passenger Side Clip (Diff Side) - QTY 1
• MB526189 - (M/T) Passenger Side Clip (Diff Side) - QTY 1
• Milner Offroad CV Boots - QTY 2

*Note that my diff is an A/T. If you have an M/T your parts and mileage may vary.

RESOURCES

• How to Install an ARB Air Locker (Very Detailed!) - YouTube
• DIY 2021 Toyota Tacoma Gears and Locker Install! 5.29 Yukon Gears And ARB Lockers In My 3rd Gen Taco - YouTube
• Diff rebuild - how to set pinion bearing preload Ep.1 #1023 - YouTube (part 1 of 4)
• Install a Locking Rear Diff - The Mostly Correct Guide - YouTube
• How Long Will The Rudicon Be 1/2 Dun? - YouTube
• Mitsubishi Workshop Manual – Section 26 – Front Axle
• TRE Manual

The first three videos, six if you count the other 3 parts of video 3, were super helpful with good information. #4 and #5 were helpful in just seeing that it's not rocket science. In the case of Matt’s Offroad Recovery, you can see these guys are just clowns doing the work, makes me feel better about my ability to get it done.

A final note, I will continue to update part #’s as I get more worked out. Anything in RED is still questionable. I will also begin to add a tool list that I use or accumulate along the way.

I will be taking my time in doing this install trying to break it down into several days. Seeing as this is a pretty big job and I don’t want failures while in the field. I will do my best to get it right because I really only have one shot at it.

I will begin posting in the coming days.

Wish me luck!!

 

[bikerjosh]

Exciting times.

 

[hardknockgarage888]

Very excited to see the process! Thanks for documenting!

 

[Growlerbearnz]

You also need MB185375 SPACER SET,FR DIFF QTY2
The front diff backlash (diff cage side to side adjustment) is set with shims, not adjusters like the rear diff. This is the shim kit. I'm not sure why they think you need 2 sets but Murphy's Law says if you order one set you won't have enough, if you order 2 sets you'll have too many.

Also: Following with great interest. My front Lokka has all the traction at low speed, but above 50kph on gravel it's terrifyingly twitchy. A slight imbalance of traction (packed dirt on one wheel, soft gravel on the other) and it'll yank the steering wheel to one side. A locker would solve that problem.

 

[Nenw]

Thanks Growler. I saw that Mitsubishi had 2 shim kits for the diff and 2 for the pinion.

The Locker came with shims, I still have yet to dig into what everything in the box is but this gives me a reason to hit this sooner and clarify. I was thinking it was for the backlash.

Looking at the Amayama Diagram, I thought Shim set C was to set backlash within the carrier and that Shim Set D was for the little spinny gears within the open diff mechanism. I don't have all technical terms so you'll have to excuse me.

My plan, after I took my initial measurements from the stock setup was to pull the diff and ensure the ring gear would mount and that the locker would in fact install. Then I was going to go ahead and order up all the parts.

 

[13mclean]

The shim sets get especially confusing when Mitsubishi epc and amayama have different diagrams and labels…

 

[13mclean]

At a glance, MB185375 looks similar to the shim set included with the locker.

 

[13mclean]

TRE spacers

 

[Growlerbearnz]

Shim set A is for the overall ring gear/pinion backlash (goes between the bearings and the case.) That TRE shim set does look about the right size to be set A.

 

[Nenw]

This is exactly why I was going to do a quick pull apart of things before I dropped my order.
Thanks for looking out guys!

 

[Sputnik]

Looks like an awesome project! You're brave, but also very organized, and a good plan is half the battle.

Also, that CV boot link is a cross reference paradise, so thanks.

 

[Nenw]

STEP 1: OPENING AND MEASURING THE OLD STUFF

I opened the diff and was not too impressed with what I saw. First off, it was pretty grungy in there. The diff oil was definitely contaminated and kind of dark. I also found some metal shavings.

My buddy never changed the oil himself but is certain the shop he bought it from did. Uh huh, yeah surreee...
Perhaps he ran through a puddle and got some water in there or something bc it definitely was not clean.



Additionally you can see quite a bit of damage do to the outer edge (heal) of the ring gear.
Depending on how the pinion looks I may not worry too much about it.



The drive and coast patterns were definitely out of spec.
The drive side (Left Pic) was a little far to the heal of the ring gear and the coast side (Right Pic) was a little too far to the toe.
Shame on you Mitsubishi!



At least the backlash was within spec albeit barely.
Just a smidge over .006". Spec range is (0.0043"-0.0063")
Cutting it close there.


I was really hoping to have a solid baseline and a good picture of what good looked like. Perhaps having things be somewhat out of spec is a better lesson.

In the meantime, anyone with experience here 'cough' growler 'cough' sk...have any thoughts on the condition of the ring gear?
I'm thinking not a big deal if the pinion is looking good and I can get it back together better than Mitsubishi.

If there is concern here, I suppose I can always tear into the one off my van. Perhaps the benefits of working from a donor diff!

Thanks y'all.

 

[Growlerbearnz]

Got a clearer and cleaner photo of the drive side tooth face? It looks like there might be some pitting on the heel, but if you improve the contact pattern it shouldn't be a problem.

Ok those photos are better. It's had some particles through it but it doesn't look ruined to me. No deep scoring, glazing, or burning. Unless the pinion is knackered (unlikely) I'd be comfortable re-using that gearset. The front diff doesn't do 60+mph for hours on end, so a little imperfection is acceptable. Getting the contact pattern right will shift the pressure away from the worn patches anyway.

It looks to me like the pinion depth is correct and you only need to fix the backlash (shims beside the main bearings) to get that contact patch perfect. I would still change the pinion bearings, but keep the original pinion preload/height shims and see how that goes. If you change too many things at once you can end up chasing your tail.

You'll set up the preload as per the workshop manual, right? A digital torque wrench is good for measuring the pinion turning torque.

 

[The Tick]

Following.

 

[kbrown934]

Good Luck, I love gears and will be folowing your adventure. Kevin

 

[Nenw]

@Growlerbearnz - Added better pics of the drive and coast edges to the previous post. Looking closer at it I am much less worried and it seems that the drive side heel is not as chunked up as the coast side heel. I will still be sure to inspect the pinion closely when I pull the diff apart.

The other thing to address is the backlash shims that we discussed earlier. I measured each shim that came with the locker in three spots and noticed that they were not a constant thickness. I understand there will be some tolerance, but what is acceptable?

I also noticed that there were some finish issues around the outer edge, and the thickest shim was a little sloppy at the weld.
I may just get the Mitsubishi shims or see what ARB has.

Here's a measurement table that I slapped together. In the final two columns, you can see the variance in thickness between the thickest and thinnest measurements. The final column is the percentage change in dimension referenced against the smallest measurement. It is the tolerance.

When you see a 4/1000" inch change it doesn't seem like all that much but when that shim is only supposed to be maybe 1/100 of an inch thick you realize there is an issue.

Additionally, I am guessing the shims should be paired .01", .02", .03", .07"
If this is the case you can see there are some consistency issues in the cuts.

Shim	Measurement 1	Measurement 2	Measurement 3	Variance	Variance as a Percentage of thinnest dimension.
1	0.0088	0.0083	0.01	0.0017	20%
2	0.0091	0.00815	0.0122	0.00405	50%
3	0.01915	0.01935	0.0191	0.00025	1%
4	0.01945	0.0198	0.0191	0.0007	4%
5	0.03345	0.03265	0.03275	0.0008	2%
6	0.033	0.0333	0.0333	0.0003	1%
7	0.07965	0.07995	0.08695	0.0073	9%

 

[delicadenny]

Awesome! I've been wanting to order the TRE one for mine, but they couldn't confirm whether it was going to fit or not. Thanks for taking the leap

 

[Nenw]

Okay y'all, I am back at it after breakdowns, personal travel, business travel, personal covid, and shortly to get the boot from my rental. I have to make this happen.

I have received and measured a set of ARB shims and these are much MUCH better than the TRE ones. Will it make a difference in the end? Who knows. But I feel better about it. In chatting with a Luso Overland, they did mention a shop in AZ has some experience with the TRE stuff and mentioned they require a bit more shim work than ARB to get things dialed. Let's hope better-cut shims make a difference.

Additionally, I am working on getting new o-rings to go into the Air Seal mech. I misstated the o-ring size in the initial post. I have done a ton of work to try to find the correct size. I lost a spare o-ring when a local shop said they would shoot one to their o-ring maker to size up and test the hardness, but ended up dropping the ball and losing it. I had Luso reach out only to be shot down by TRE to grab the spec. I even went as far as having a friend write to TRE in Chinese, hoping they would hook a brother up! In the end, I measured and printed an o-ring sizing tool. I will be able to confirm the size and fit once the new o-rings arrive next week.

The reason for all this is because the o-rings are ity bity. 2mm in width versus the ARB which are fractional but equivalent to 2.6mm in thickness. That's 25% thicker. That's more material and more sealing surface. ARB on more recent lockers have moved to x-profile rings as well. I want to ensure I have the highest quality $2 o-ring in there. I found a USA-made one that is ASTM qualified, meaning it has to meet minimum requirements when subject to heat and chemicals. So many out there are not qualified, which may not be an issue but again, why throw in a questionable $2 part. Plus when I called to ask, the inside rep just sent me a test report. Amazing. They will have all my $2 o-ring business from now on. See attached if you want to geek out on an o-ring test report.

Lastly, I've begun printing seal and gasket presses bc why not? I've been wanting to learn CAD and this turned out to be a wonderful exercise. Lots of repetition in drawing circles on top of circles and extruding them. I will make these available when I verify they don't get stuck into whatever I am pressing in. And If you want your very own set but don't have a printer, just hit me up, I will also make them available for sale.

This was all a long-winded way of saying, things are beginning to move along.