Will the 4.7 final drive ratio kill MPG and TOP end speed for use as practical daily driver?

[Rydfree]

New to understanding this stuff but I get this;

3.73 RATIO	4.10 RATIO
Slower off the line	Quicker off the line
Lower torque	Higher torque
Better gas mileage	Worse gas mileage
Higher top speed	Lower top speed

So does that mean 4.7 on the Bandlands is a killer for a daily commuter?

It will be fine , especially if you have the 10 spd Auto . There are plenty of gears to choose from and the computer will simply put you in a higher transmission gear on the hwy .

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[Nicksuccarotte]

I went from 3.31 to 4:10 on my 14 F150 with 5.0 and my mpg in the city actually got better. The 4:10 allowed the auto transmission to shift into 6th in the city. Normally it stayed in fifth. Hwy MPG only went down 2.

Everything depends on the gearing in the transmission. A 10 speed in the Bronco will help a lot with mpg.

That makes since and most my driving is highway driving so that could be why I noticed a difference, but I if I had to guess a non squatch with lower gear and smaller tires would probably get overall better mpg, but i could be wrong but we will see, I mean I hope not because that would be better for me and alot of us lol

 

[Stitches1974]

And real world numbers on the rubi are closer to 15/18-20. Those numbers are from low resistance straight line driving. Put them into real world scenarios and you’re closer to the low side. I would bet more realistically on 15/18-20.

Granted the rubi has 4.10 gears, this is a Willys with 32 inch tires, with 3.73 gears, and 5 speed auto. The new 8 speed auto should improve MPG some.

 

[Charky]

As has been previously mentioned, these vehicles have the aerodynamics of a brick and a significant impact on your highway mpg is how fast you drive. I wasn't immediately able to put my fingers on it, but in another thread of similar discussion, some folks with an engineering background went into all the math and just 5 mph one way or the other is a huge deal.

At 15,000 miles driven per year, $2.75 per gallon and 20 mpg compared to 17 mpg, the annual cost difference is $365 per year, or $1 per day. Of course this cost changes with miles driven per year and fuel cost, but you get the point. It's not a huge expense.

Just get the gearing and tire size you want and that best fits how you're going to use your Bronco, put your foot into it and enjoy the ride! Put an emphasis on smiles per gallon! ?

 

[Willwork4bronco]

Yea but when you add bigger tires doesnt your MPG drop lower also?

Maybe im not understanding something here, in my experience changing to a higher number gear 4.10 or 4.7 hurts your fuel economy, also the bigger your tires are 33 to 35inch hurts your fuel economy so why together would it be a wash? I'm not a mechanic but my simple logic would tell me together they would make your fuel economy even worse not wash each other out. But please let me know if my understanding is wrong.

No you pretty much got it. It’s going to depend on the driving conditions and speeds more than any thing else. Lower gears (higher number) are always going to result in a loss of MPG at a constant rpm. Now go with completely city driving stop and go all the time and there could be an increase simply because you never get into a steady rate and the engine doesn’t have to work as hard to get you moving.
Now with tires there is absolutely no way possible a bigger heavier wider tire is going to increase MPG. Well unless 100% of your driving is down a 6% grade and the weight helps gravity pull you down the hill. I think what the comment about it being a wash was was more geared to changing the tires. Say changing from 33 to 35 drops total MPG by 2. And changing gears drops total MPG by 2. If you do both at the same time you don’t get a drop of 4, maybe just a drop of 3 because 50% of the drop from tires was simply because the engine had to work harder to get the wheels started and keeping them moving. When you add the gears you give it a mechanical advantage so the engine doesn’t have to work as hard to do the same. The difference between BL 4.46 w/ 33s and a BL with 4.7 and 35s is probably pretty negligible. Now the difference between a Base with 3.73 and 31’s and that BL Sasquatch definitely warrants some consideration.

 

[Nicksuccarotte]

No you pretty much got it. It’s going to depend on the driving conditions and speeds more than any thing else. Lower gears (higher number) are always going to result in a loss of MPG at a constant rpm. Now go with completely city driving stop and go all the time and there could be an increase simply because you never get into a steady rate and the engine doesn’t have to work as hard to get you moving.
Now with tires there is absolutely no way possible a bigger heavier wider tire is going to increase MPG. Well unless 100% of your driving is down a 6% grade and the weight helps gravity pull you down the hill. I think what the comment about it being a wash was was more geared to changing the tires. Say changing from 33 to 35 drops total MPG by 2. And changing gears drops total MPG by 2. If you do both at the same time you don’t get a drop of 4, maybe just a drop of 3 because 50% of the drop from tires was simply because the engine had to work harder to get the wheels started and keeping them moving. When you add the gears you give it a mechanical advantage so the engine doesn’t have to work as hard to do the same. The difference between BL 4.46 w/ 33s and a BL with 4.7 and 35s is probably pretty negligible. Now the difference between a Base with 3.73 and 31’s and that BL Sasquatch definitely warrants some consideration.

Ok thanks, that all makes since, I appreciate your insight.

 

[mrcx]

My last Wrangler was a manual with 3.21 gearing (I think, might have been 3.73), I don't remember for certain. But 6th gear was pretty much unusable. I'd have to be going at least 75 to even think about shifting into 6th. And then I couldn't pass anyone, drive into a decent head wind or go up any kind of incline without shifting back down into 5th. I wouldn't want another one unless it had at least 4.70. A lot of Jeep owners will re-gear to 5.13.

If you get the 3.73 gearing, you are quickly going to wish you had the 4.70. Especially if you end up putting 35's or larger tires on it.

Couple if things I've never heard anyone say. 1) I wish I had a smaller engine (less horsepower) or 2) I wish I had less torque (higher gearing).

 

[Willwork4bronco]

Ok thanks, that all makes since, I appreciate your insight.

There is one other thing I didn’t mention and someone will probably bring it up just to say I told you so.
A larger wheel does have a lower revolution per mile that would result in a lower engine RPM. So there is a possibility that if you did 98% cruising on the highway on flat ground and did not change the gears you might see an increase in MPG but probably not noticeable as most of that would be off set by the increased rolling resistance of the weight and friction (because the tire is usually wider). Even the slightest incline is going to but you back in the negatives again.

 

[Chuck_Ruck]

My last Wrangler was a manual with 3.21 gearing (I think, might have been 3.73), I don't remember for certain. But 6th gear was pretty much unusable. I'd have to be going at least 75 to even think about shifting into 6th. And then I couldn't pass anyone, drive into a decent head wind or go up any kind of incline without shifting back down into 5th. I wouldn't want another one unless it had at least 4.70. A lot of Jeep owners will re-gear to 5.13.

If you get the 3.73 gearing, you are quickly going to wish you had the 4.70. Especially if you end up putting 35's or larger tires on it.

Couple if things I've never heard anyone say. 1) I wish I had a smaller engine (less horsepower) or 2) I wish I had less torque (higher gearing).

My 06 F150 has the 4spd auto, and 3.08 gears. Now the state of NY has a max limit state wide of 65mph so I hardly ever have the truck in top gear. That being said it gets 13mpg on average, but going through TX on I-10 where you can legally do 80mph, I get about 24mpg on average. My 98 F150 has the 5 spd manual w/ 3.08, and it gets 26mpg at best, but again at higher speeds I have seen it get 34mpg.

 

[GoldenKnight]

As has been previously mentioned, these vehicles have the aerodynamics of a brick and a significant impact on your highway mpg is how fast you drive. I wasn't immediately able to put my fingers on it, but in another thread of similar discussion, some folks with an engineering background went into all the math and just 5 mph one way or the other is a huge deal.

At 15,000 miles driven per year, $2.75 per gallon and 20 mpg compared to 17 mpg, the annual cost difference is $365 per year, or $1 per day. Of course this cost changes with miles driven per year and fuel cost, but you get the point. It's not a huge expense.

Just get the gearing and tire size you want and that best fits how you're going to use your Bronco, put your foot into it and enjoy the ride! Put an emphasis on smiles per gallon! ?

For just one dollar a day, you could feed a Bronco

 

[Gquag]

New to understanding this stuff but I get this;

3.73 RATIO	4.10 RATIO
Slower off the line	Quicker off the line
Lower torque	Higher torque
Better gas mileage	Worse gas mileage
Higher top speed	Lower top speed

So does that mean 4.7 on the Bandlands is a killer for a daily commuter?

It is correct for 35" tires. If you reduce the tire size it will wind out/up sooner. I had the same question so if searched for a chart.

 

[Gquag]

New to understanding this stuff but I get this;

3.73 RATIO	4.10 RATIO
Slower off the line	Quicker off the line
Lower torque	Higher torque
Better gas mileage	Worse gas mileage
Higher top speed	Lower top speed

So does that mean 4.7 on the Bandlands is a killer for a daily commuter?

It is correct for 35" tires. If you reduce the tire size it will wind out/up sooner. I had the same question so if searched for a chart.

 

[WatchYourSix]

@Gquag That is great, thank you. I find it easier to read on the site though.

https://www.usgear.com/usg-admin/resources/literature/ratio-chooser-chart.pdf

 

[ramblinwreck]

@Gquag That is great, thank you. I find it easier to read on the site though.

https://www.usgear.com/usg-admin/resources/literature/ratio-chooser-chart.pdf

I’m not sure how useful this chart is. You need to know the final drive ratio, including transmission gearing. The 10A has quite the spread on gears.

 

[WatchYourSix]

I’m not sure how useful this chart is. You need to know the final drive ratio, including transmission gearing. The 10A has quite the spread on gears.

Ballpark figures though, no?

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