Re-Gearing (1 Viewer)

Joined
Oct 28, 2020
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Virginia
I have a 2015 SR5 with Bilstein 5150 and OME rear Springs running 32.76" Nitto Ridge Grapplers on stock 17x7 rims. My question is, do I need to re-gear? I also have full RCI plating, LFD Roof Rack, and SSO Rock Sliders so some added weight but not a ton... I'm currently getting between 15-17 mpg... Would there be any mpg benefit to re-gearing?
IMG_0371.jpg
 
Joined
Sep 16, 2004
Messages
1,359
Most likely it'll go down. I've had both 285/70/17 (32.8), 275/60/20 (33.01), and 285/75/17 (33.9) tires. And both 3.73 and 4.56 diffs. 4.56 diffs got worse mpg in all cases.

My opinion is that 4.56 is too low for the efficiency of the 1gr with the 5 speed transmission. It's the right gearing for 37-39 inch tires. It's really the transmission holding us back though. And its really frustrating to me. The 5 speed has 6 gears. It uses the same gear train as the 6 speed, but only shifts into the first 5 gears. The 6 speed has a different valve body and one more internal clutch so it can shift to all 6 available gears. If we had the 6th gear (a second overdrive), then 4.56 would be perfect all around. But Toyota gives zero f***s about the USA market 4runner. So they can't even be bothered to put the 15 year old 6 speed parts in the 6 speed transmission we already have to let us use the extra gearing.

I have also talked with Circle K in Korea about making some 4.10 diff gears. They can do it with existing forged blanks they already make. Deal breaker for me was the 200 set minimum order. But 4.10 gears would be ideal IMO for 33-34" tires. If I thought I could sell enough sets, I'd order them. But I'm not in the business of selling car parts. I'm surprised someone isn't selling them though. The gross margin on gears is over 100%. - point being that circle k makes all aftermarket 8.2 gears, they can cut 4.10 sets, but no one has ponied up to have a run made.

FWIW - I took the 4.56 gears out and went back to 3.73. I still have both sets. 4.56 was better on trails and in town. 3.73 was still better on the highway and oddly better for towing (because I'd be in 4th gear either way, so 3.73 had lower rpms).
 
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CreeperSleeper

Cascade Cruisers
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Forest Grove, OR
Most likely it'll go down. I've had both 285/70/17 (32.8), 275/60/20 (33.01), and 285/75/17 (33.9) tires. And both 3.73 and 4.56 diffs. 4.56 diffs got worse mpg in all cases.

My opinion is that 4.56 is too low for the efficiency of the 1gr with the 5 speed transmission. It's the right gearing for 37-39 inch tires. It's really the transmission holding us back though. And its really frustrating to me. The 5 speed has 6 gears. It uses the same gear train as the 6 speed, but only shifts into the first 5 gears. The 6 speed has a different valve body and one more internal clutch so it can shift to all 6 available gears. If we had the 6th gear (a second overdrive), then 4.56 would be perfect all around. But Toyota gives zero f***s about the USA market 4runner. So they can't even be bothered to put the 15 year old 6 speed parts in the 6 speed transmission we already have to let us use the extra gearing.

I have also talked with Circle K in Korea about making some 4.10 diff gears. They can do it with existing forged blanks they already make. Deal breaker for me was the 200 set minimum order. But 4.10 gears would be ideal IMO for 33-34" tires. If I thought I could sell enough sets, I'd order them. But I'm not in the business of selling car parts. I'm surprised someone isn't selling them though. The gross margin on gears is over 100%. - point being that circle k makes all aftermarket 8.2 gears, they can cut 4.10 sets, but no one has ponied up to have a run made.

FWIW - I took the 4.56 gears out and went back to 3.73. I still have both sets. 4.56 was better on trails and in town. 3.73 was still better on the highway and oddly better for towing (because I'd be in 4th gear either way, so 3.73 had lower rpms).

This is all really interesting... I forgot, what are you towing with your Runner?
 
Joined
Sep 16, 2004
Messages
1,359
This is all really interesting... I forgot, what are you towing with your Runner?
A HUGE 10 foot long teardrop camper. 🤣 My biggest issue is that I tend to drive too fast. Generally I found that with 4.56 gears and even my little trailer I couldn't hold 5th gear on flat ground at 65mph. And being in 4th with 4.56 meant it drop down to 11mpg towing and around 15-16 highway empty. With the 3.73 I get more like 13-14 towing and about 18 highway empty. It's about the same with either 33" or 34" tires.

4.56 feels so much better. But the fuel burn tells me the engine is working harder or is outside of the higher thermal efficiency range. I think the 1gr is tuned to run really rich at higher rpms. It never overheats or has any issues. Just sucks down fuel like a big v8 but without any of the power.

I recently bought a diesel f250, so this might all be meaningless for me as far as towing goes. But I'm keeping the 4runner because it's still far better as a daily driver and adventure vehicle. It's actually just a better vehicle period. But it's not the right one for towing and hauling.

If I had the time I'd love to swap in a a760f transmission. They're a direct bolt in and share the same housing - because they're essentially the same transmission. I don't know enough about the ecu to know if it's doable to make the engine and 6at play nice together. Toyota does use the 6at behind the same 1gr in the same 150 platform in other markets. So it might be a matter of finding the right ECU that's already available. Might even be as simple as plug and play. But then... Why not just trade for a GX? It's cheaper and easier.
 
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Lexington KY, Boston MA
But Toyota gives zero f***s about the USA market 4runner.
I don’t disagree with what you said about a six speed being ideal for a modified 4Runner, but the 4Runner is almost exclusively a US market vehicle, and has not ever been made with a 6 speed auto in any market.

The closest thing I know of would be the AC60F in the tacos +2016 or whenever they went to the new engine, and I wouldn’t be surprised if that makes its way into a update for the 4Runner model. The 5th gen 4Runner with the A750F as we know it pre-dates the 6 speed in similar chassis, and that is why it is behind on that.

It makes sense when you think about it. It’s not because Toyota holds a world war grudge or anything lol
 
Joined
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Here's my issue. The same factory that builds the 4runner also builds the same chassis (not exactly but very very similar) for the Prado 150. And in that same factory they manufacture a prado 150 with the 1GR and the A760f. They also build a prado 150 with the 3.5l ac60 for Asian markets. The AC60 is an updated A760. And they also manufacture the Prado with the v8 and a760f. So every gas engine that's offered is already matched with the 6AT in the same platform in the same factory. It's just a matter of choosing the transmission from the parts bin. 6AT or 5AT. And the 4Runner gets the 5AT while everyone else gets a 6AT.

And the a750 was always a 6 speed internally. It was almost certainly engineered from day 1 as a 6 speed, (or a very lucky coincidence that the same internals randomly had a 6th gear that only required different solenoid engagement pattern to use). And internally the A750F has all 6 gears in the gear train. It just isn't setup to shift into all 6.

From where I sit - I see that every 150 platform for every market I know of gets a 6AT except the 4Runner. And the 4Runner is actually the more expensive of the twins in markets where the Prado 150 and 4Runner are both sold, - how is it that the 4Runner still gets the 5AT? I can only conclude that Toyota just doesn't care. I'm pretty confident Toyota could figure out how to put the 6 speed version of the same transmission in a 4Runner with almost no effort if anyone at toyota cared even a tiny little bit about it. And they also already have 4.56 gears for both diffs in the parts bin. That also should be a non-issue. Toyota claims that the 6AT is 8% more efficient in other models than the 5 speed because of the extra gear range. If the 5 speed still soldiering on in the 4Runner isn't the result of apathy toward the product - I really can't think of another logical explanation.

You can look through part by part yourself if you're super bored:
a750.jpg

A750F_scheme.jpg
 
Joined
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Messages
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Lexington KY, Boston MA
Here's my issue. The same factory that builds the 4runner also builds the same chassis (not exactly but very very similar) for the Prado 150. And in that same factory they manufacture a prado 150 with the 1GR and the A760f. They also build a prado 150 with the 3.5l ac60 for Asian markets. The AC60 is an updated A760. And they also manufacture the Prado with the v8 and a760f. So every gas engine that's offered is already matched with the 6AT in the same platform in the same factory. It's just a matter of choosing the transmission from the parts bin. 6AT or 5AT. And the 4Runner gets the 5AT while everyone else gets a 6AT.

And the a750 was always a 6 speed internally. It was almost certainly engineered from day 1 as a 6 speed, (or a very lucky coincidence that the same internals randomly had a 6th gear that only required different solenoid engagement pattern to use). And internally the A750F has all 6 gears in the gear train. It just isn't setup to shift into all 6.

From where I sit - I see that every 150 platform for every market I know of gets a 6AT except the 4Runner. And the 4Runner is actually the more expensive of the twins in markets where the Prado 150 and 4Runner are both sold, - how is it that the 4Runner still gets the 5AT? I can only conclude that Toyota just doesn't care. I'm pretty confident Toyota could figure out how to put the 6 speed version of the same transmission in a 4Runner with almost no effort if anyone at toyota cared even a tiny little bit about it. And they also already have 4.56 gears for both diffs in the parts bin. That also should be a non-issue. Toyota claims that the 6AT is 8% more efficient in other models than the 5 speed because of the extra gear range. If the 5 speed still soldiering on in the 4Runner isn't the result of apathy toward the product - I really can't think of another logical explanation.

You can look through part by part yourself if you're super bored:
a750.jpg

A750F_scheme.jpg
Cool exploded parts diagram! I do like reading into thing like this.

I believe the 750 had been around for 5-7 year in the 4Runner by the time the 760 started being used in a 150 chassis.

I guess what I was getting at is, I’m sure they know from an engineering standpoint what transmission would be ideal...but change is slow to happen on the manufacturing side. And in stock form, which is really their only consideration, the 5 speed fits the bill just fine.

But I’m just a dork who spends my free time thinking about this random shyt 😂 so I have no idea really.
 
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Messages
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I own a 2011 T4R SR5 that I purchased used in 2014 with 28 K miles on the clock. Right after the purchase I added an ARB front bumper, ComeUp winch, dual battery tray, and an OME medium duty spring/shock system. I originally installed Cooper STMaxx tires at 255/80R17 33” tires. Also had 4.56 Nitro gears installed. Since then I’ve go to 255/75R17 KO2s which are approximately 32” tall. My mixed mileage, sans towing averages 15.5 mpg. On the highway/back road and towing my Mission Overland Summit trailer mileage drops to 12 mpg or less. without the trailer it can be as high as 17-18 mpg on the highway. A lot of my towing miles are in the mountains. I reall like the 5.46’s and now have over 100 K miles on them. If doing lots of hard climbing I’ll pull over occasionally to let the tranny to cool down a bit.

I have to say that on occasion I think of getting something newer, but just can’t justify it. This setup works for me. The stock gearing is great for soccer moms, but the 4.56 setup does the trick when towing in the back country and mountains. And you’re right, more gears in that tranny would be nice. Six o.k., 8 even better.

78BEF38E-4A30-4714-951F-F90017EC3C50.jpeg
 
Joined
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Messages
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fwiw - I have towed my bigger trailer with the 4R too. It's okay. Not ideal - but it has no problem maintaining highway speeds. It's about 4600lbs. 4.56 might be better if I were towing it regularly.
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The 5AT didn't really bug me as much until the Bronco was announced. And I found myself recognizing how badly Toyota has neglected it's BOF product line. And while I'm bitching about it - My RX350 has 4.40:1 diffs and a dedicated transmission cooler with it's own air intake. And it doesn't even come with a trailer hitch. It does tow better. I've towed my little teardrop with both. The 3.5L/6AT pulls better than the 4.0/5AT. The chassis isn't nearly as confident towing, but the engine/transmission combo works better.
 
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CreeperSleeper

Cascade Cruisers
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I'm in the boat of pulling a bigger trailer. The 4Runner does fine, even over the Oregon passes, but I think lower gears are needed. She's pretty heavy with all the armor. I also want to bump up the tire size to a 34x10.50, so there is that too. I just need to decide if 4.56 or 4.88 would be ideal in my situation.

IMG-20190504-101849-727.jpg
 
Joined
Oct 28, 2020
Messages
27
Location
Virginia
Most likely it'll go down. I've had both 285/70/17 (32.8), 275/60/20 (33.01), and 285/75/17 (33.9) tires. And both 3.73 and 4.56 diffs. 4.56 diffs got worse mpg in all cases.

My opinion is that 4.56 is too low for the efficiency of the 1gr with the 5 speed transmission. It's the right gearing for 37-39 inch tires. It's really the transmission holding us back though. And its really frustrating to me. The 5 speed has 6 gears. It uses the same gear train as the 6 speed, but only shifts into the first 5 gears. The 6 speed has a different valve body and one more internal clutch so it can shift to all 6 available gears. If we had the 6th gear (a second overdrive), then 4.56 would be perfect all around. But Toyota gives zero f***s about the USA market 4runner. So they can't even be bothered to put the 15 year old 6 speed parts in the 6 speed transmission we already have to let us use the extra gearing.

I have also talked with Circle K in Korea about making some 4.10 diff gears. They can do it with existing forged blanks they already make. Deal breaker for me was the 200 set minimum order. But 4.10 gears would be ideal IMO for 33-34" tires. If I thought I could sell enough sets, I'd order them. But I'm not in the business of selling car parts. I'm surprised someone isn't selling them though. The gross margin on gears is over 100%. - point being that circle k makes all aftermarket 8.2 gears, they can cut 4.10 sets, but no one has ponied up to have a run made.

FWIW - I took the 4.56 gears out and went back to 3.73. I still have both sets. 4.56 was better on trails and in town. 3.73 was still better on the highway and oddly better for towing (because I'd be in 4th gear either way, so 3.73 had lower rpms).
Wow - thank you! I do most of my driving in town lately with covid restrictions being what they are, but would prefer to have better highway mileage so this was really helpful!
 

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