We discussed this issue a few weeks ago and I've had stock and 4.56 gears. I found the 4.56 to be too low for me running mostly stock setup with 33 or 34" tires. I think 4.10 would be a good choice for heavy stock rigs, towing with stock tires, and lighter weight setups with slightly larger tires.

Just for the basic math - getting back to exact stock gearing, you'd run a 38.6" tire with 4.56 gears. With 4.10 gears, you'd exactly match stock gearing with 34.7" tires. With typical 285/70/17's, 4.10 diffs would net you approximately 5% gear reduction vs stock. With 285/75/17 - you'd be just slightly lower geared than stock.

For heavy rigs with big tires - 4.56 is often a better choice. But for the moderate setups that do a lot of highway time, I think 4.10 is a better ratio. At least it would be for me.

I reached out to a few gear manufacturers. The only aftermarket gears I think are currently made by Circle K in Korea. I think they make all of the gear sets for every brand of aftermarket gears for the rear 8.2 diff. There are currently OEM front 4.10 gear sets. So this is just for the rear.

Earlier this week I received confirmation that they believe that they can use the T8.2 forgings already in use for the other gear sets to machine for a 41 tooth pinion and 10 tooth ring. So this would be a matching 4.10 gear set to the OEM front 4.10 gears.

(They can also probably make a 4.30 set, but it's not as close to the mid point between 3.73 and 4.56 that exist already, and I'm sure a 4.11 set is also possible, but 4.11 is a weaker ratio with only a 9 tooth pinion; 4.10 is stronger in most differentials and matches the 4.10 8" clamshell front ratio already available.)

The tooling setup cost isn't as horrible as I thought. So I can get them to cut me a set of one-off samples at higher price per/unit and I can test them - by that I mean put them in a diff and make sure they setup correctly and fit, etc. I can't really "test" them for strength or durability. This is basically a proof of concept for the use of the existing forgings and making sure spacing fits and such. I don't have the ability to run them for millions of test miles, shock load them in a measurable way. I'm probably not all that interested in sending them for metal lab analysis either. I just don't really care that much to be honest. And they're a top tier gear maker and they should be the same forge stock as all the other aftermarket sets. I've used their gears before and currently have a set in my garage setup in an T8.2 elocker diff.

So... they've also said that they can produce them if there's enough interest. The minimum order quantity for production level pricing will be a few hundred sets. I was hoping for more like 50 sets and I'll see if I can make that happen, but I'm not completely sure if there's enough interest even for that many sets. I suspect it may actually be more popular for the GX crowd. I think a stock GX would benefit in a lot of ways from this ratio. But also - remember that I'm not in the business of selling car parts. I have a full time job. I don't want to deal with customer service. I don't want to warranty your junk. This would be an as-is deal. You get what you get and you take your chances. If I can get Nitro or ECGS or someone to take half the first order or something like that, maybe there could be a better option? Not sure. For now - consider it as a no-service type situation. You get the matched gear sets and they get to your door in good condition. That's all.

The upshot here is the pricing could be pretty good. Depending on volume I think I could get the gear set alone (no other parts, no shims, no crush sleeve/spacers, no loctite, no paint, etc.) - pricing down somewhere under $200 per set including repackaging and shipping to you.

You'd have to source your own mini or full install kits. Although the gears are the same, the setup is different for elocker and non-elocker. T8.2 e-locker diffs require only pinion shims. T8.2 non-elocker diffs do required carrier shims as well.

So - I guess the end of this post is that I'm not a vendor. They are not for sale. And I probably won't order a batch. I wanted to bring this back around to close the loop that - yes, circle K will make them and they would not cost all that much if there was enough market.

So what do folks think? Is this something that would be worth a group buy of some sort? Is it something you'd want if I/we could convince a vendor to carry them with full service behind it instead if they were more like $350/set? Or is this a ratio only I want and I should just order a one-off set for me that I might never install if I sell my 4Runner before I get around to it?

@Jetboy this is amazing and thank you for your hard work. I'm somewhat confused by the tire sizes you listed, could you clarify they are correct?


This will be a great option for quite a few people!

No problem. I haven't actually done much work. Just tracked down the manufacturer in Korea and figured out how to get in contact with the right person and then asked what it would take to make it happen. They were happy to look into it. Just took a bit of time to look into it and get back to me. Funny thing is that none of the USA manufacturers of gears responded at all. Not interested.

Anyway as far as the ratios go - you can double check my math, but I think it's correct save for some rounding errors:

(31.6 / 3.73 = 38.6 / 4.56)

and

(31.6 / 3.73 = 34.7 / 4.10)

31.6 / 3.73 = [(32.7/4.10) * 1.05]

I must be confused. I'm reading a 38.6" tire with 4.56 gears is the same as stock gear ratio?



I clearly don't understand the analogy. And your math is always impeccable so I must not be able to wrap my head around what your saying


Edit: Never mind me, I see now

I screw up on math all the time. I just never admit it... lol.

I was just calculating the net ratio of something like distance traveled per revolution of the drive shaft. I don't think most people are best served by getting back to the same ratio as stock. Especially if you've got a lot of extra weight and rolling resistance, you probably want something that nets a ratio lower than stock to also makeup for the higher load. I just use that as sort of a reference point to start considering where I'd want to be and choose the closest ratio that's lower.

Yes that's where my mind was going, I was thinking of the the circumference not the tire size, however, I see the analogy now.

I've been trying to get smarter on gearing, but I'm not sure I can see the value in 4.10.
I agree it should have been the stock gearing.
But no one modding for off road would want something so low.
As soon as you add bigger tires, weight, all you are getting is back to stock - stressing highway fuel economy, not more performance/power.
4.10 makes sense if you stay stock, but who "stays stock" and re-gears.

I'm not sold on the RPMs with 4.56 yet, but I'm still running 265 for now.
I'm also hesitant to do a BMC (I have issues messing with safety features).
I may end up doing nothing, but I don't see the attraction to go "only" to 4.10.

I'm torn and based on previous info from @Jetboy I was starting to ponder the LC rear axle at some point plus a Tacoma front diff - the whole setup could possibly be obtained for under $1K before selling OEM stuff.

I daily my rig hard (30K/year) and offroad maybe once a month (more would be ideal, but life happens). I'm okay with the 3.73's with 255/80s and I'd like to bump up to 285/75 for my next tires, but there is hesitation on doing this with 3.73s. Going to 4.56's isn't very appealing as I do a lot of highway driving 75+ MPH and I worry the drive-ability at these speeds would be reduced.

Obviously if someone had done some trial driving and could confirm it wouldn't be for waste (someone who had driven stock, 4.10, 4.56) that would really help sell the deal.

Thanks for all the research into this @Jetboy !

I see you're in Monument, I'm in Lone Tree. Would it be helpful to take a drive in my rig?
I think ultimately you're right, that 4:56 won't be great for going 75+ in a built rig (especially in Colorado), however there are a lot of other pluses. I can tell you that when I first went to 285/75's my rig wasn't very heavy and stock gears were miserable so like all things it's a trade off.

I’m in for some 4.10 gears

We might need to meet up, I appreciate the offer!!

4.10s, would be pretty awesome for sure.

Definitely need some 4.1, i have 285/75r17 and i can definitely feel the need for gears even with my supercharger already.

maybe convince ECGS to get these and sell complete units hah

I put 4.10's in my GX on 34's but that's easy since it's a 8" ring gear and with some case mods you can install a Tacoma elocker. Front gears are available for the 8" clam shell, which is the same or similar to the 5th gen.

Would it be easier to swap a 8" rear diff in from a older FJC or 4th gen to get the 4.10 ratio your looking for? Yes it's a "weaker" diff but for the mostly pavement pounders a non issue. And you get some rpm back with a 33ish tall tire.

My 5th gen on 34's isn't a rocket ship but IMO would benefit greatly from 4.88's, esp since it's going up to 35x10.5's soon.

You can order 4.30s, Manual TRD offroad tacomas come with them and have elockers