3.31 vs 3.73 gear ratio

[JasonH]

Prior to 2018, Limited and higher trims came with HD Tow, which included 3.73 on 4x4 (but not 4x2). Starting in 2018, HD Tow was an option in all trims and was needed to get 3.73 (FX4 had it too).

 

[Alex Taylor]

Great info here for a new owner thank you all again.

 

[Jeff R]

When I bought my 2020 XLT 2WD last spring, I had to compromise on some interior options in order to find a in my preferred exterior color (red) and the HD tow package. The dealer told me my vehicle was the only one in TX at the time in red with the HD pack.

The tow pack was a priority because of the LSD and the fact that I will own this vehicle for at least 10 years. I don't tow often right now, but when I do and it I do so more in the future, it is sure nice to have. I don't really care about the slightly lower mileage.

 

[Dice Roll]

There really isn’t any proof the 3.73s get lower mileage.

 

[JExpedition07]

There is, 3.73s run more RPM for the same given speed than 3.31s. More RPM burns more fuel because the injectors are firing more times per minute. Well worth the extra gas consumption to get the better gears though.

 

[Dice Roll]

There is, 3.73s run more RPM for the same given speed than 3.31s. More RPM burns more fuel because the injectors are firing more times per minute. Well worth the extra gas consumption to get the better gears though.

no, that’s a simplistic view. Lots more to it. If you are in the fuel island sweet spot it’s not going to make a noticeable difference. You can even see higher mpg with a lower gear depending on things like cam timing, converter, etc.

You won’t get ford to tell you there is a difference on the expy regarding mpg and gearing. It’s likely due to the deep overdrive using 10th more with the 3.73s than the higher gears using 8th or 9th.

 

[rjdelp7]

When I bought my 2020 XLT 2WD last spring, I had to compromise on some interior options in order to find a in my preferred exterior color (red) and the HD tow package. The dealer told me my vehicle was the only one in TX at the time in red with the HD pack.

The tow pack was a priority because of the LSD and the fact that I will own this vehicle for at least 10 years. I don't tow often right now, but when I do and it I do so more in the future, it is sure nice to have. I don't really care about the slightly lower mileage.

Dealerships lie, do your homework. I once was told by a salesman, they 'located' a vehicle, two states away. They wanted me to have it swapped to my state(for $150). I found one, 6 miles away, at a local competitor, on the lot. The payment for exact vehicle, was also, $20/a month less. Remember, your dealing with scumbags.

 

[Plati]

There really isn’t any proof the 3.73s get lower mileage.

Geez I sure can't claim to totally understand this whole thing BUT I always figured the difference was like on my bicycle ... gearing. When I get up to speed on my 15 speed bikecycle, I'm in the highest gear and the output of my engine (legs) is slightly less to stay going along at that speed than any lower gear. Certainly less crank RPM's. The lower gears are better for getting up to speed and going up a hill. I figured the difference between 3.31 & 3.73 was exactly the same. Once up to speed the Expy engine has to work a little less hard to stay there with 3.31. 3.73 gives you more power/torque (whatever) to get up to speed. Thats why 3.73 is better for towing (pulling up to speed and hills). I dunno though, I'm an amateur.

If I'm right then the achieved gas mileage is a function of the range of loads carried, spectrum of speeds and acceleration cycles run during the test route. So yeah, thats hard to prove. I mean, who would go to the trouble to prove that? If you did test and prove something, you would have to do every possible combination (infinity). Then you might be able to say that one gearing gets better gas mileage under one group of parameters (but worse in another) and vice versa.

 

[Dice Roll]

That’s exactly it. The load is the determining factor and it’s not as straight forward as if these things had a 1:1 high gear in the trans. The rpms change around so much with the extra overdrives in play. That changes the load. I haven’t pulled the gear spreads, but you could end up with a lower effective ratio with the 3.31 or 3.15 gear than with the 3.73 when it downshifts. Then you have things like the amount of boost. Just a lot of variables in the mix.

 

[rjdelp7]

I swapped the factory, pathetic 3.08 gears on my 1993 5.0l Mustang to 3.55. It was around 1400 rpm @60mph with originals and went up to 1800rpm with the 3.55. It really woke the car up 0-40mph. Fords make good power in the mid band. I was recommended the 3.73 and they would been fine. Some say, the quicker you get to high gear/overdrive is the key to good mileage. Lugging the engine in high gear at low speed causes piston slap. Having to constantly downshift for power is annoying. I say, always opt for the higher gear ratio. No matter what you drive, you will get use to the gas gauge over time.

 

[lobsenza]

A vehicle with 3.73 axle will likely downshift less often because it will be not be needed as much for power as it will be with a 3.31. The 3.73 will operate in a higher gear sooner than the 3.31 because it will require less throttle for a given level of acceleration. I doubt there will be any difference in fuel economy around town driving. There might be a slight difference in fuel economy on the highway in 10th gear. But, if it is hilly, the 3.31 will downshift out of 10th sooner than the 3.73.

I think most drivers will notice the acceleration difference, few will notice a fuel economy difference.

 

[Expedition Dave]

Lob nailed it.

That being said, there are probably some speeds/range 4/load where the 3.31s will shine, but it might be difficult to achieve. My FX4/HD tow gets 27 mpg at 70 mph (based upon info center), sea level with air and 300 lbs of me/gear, tires 34lbs.

Even if I had an identical rig (which you can't buy) I do imagine that I could see 1 more mile per gallon, but only if that theoretical truck does not downshifts a few times with the 3.31 where the 3.73s didn't.

That would level the mileage field advantage, IMHO.

 

[KJ-Idaho]

Just for the record again, Ford claims for SWB Expedition:

3.73 - 22 mpg
3.31 - 23 mpg

but, all the variables described in earlier posts affect your results.

I like to use the travel on that right side pedal.

 

[JExpedition07]

The 3.31s won’t have the EcoBoost downshifting often on the highway unladen so I maintain your MPG will be better on the highway. My 5.4 Triton with 3.73s runs up the I-190 bridges (steep) every day in 6th and never has to downshift from final gear to maintain 65. I’d imagine an EcoBoost with 3.31s won’t need to either. Very few unladen situations on the highway have you downshifting unless you have a trailer in tow.

 

[wakeboarder]

Just for the record again, Ford claims for SWB Expedition:

3.73 - 22 mpg
3.31 - 23 mpg

but, all the variables described in earlier posts affect your results.

I like to use the travel on that right side pedal.

What is the source of the different mileage based on gear ratio?

 

[Dice Roll]

Just for the record again, Ford claims for SWB Expedition:

3.73 - 22 mpg
3.31 - 23 mpg

but, all the variables described in earlier posts affect your results.

I like to use the travel on that right side pedal.

where do they list that? Only thing I’ve seen make a change on the rating is 4wd and the max.

 

[Dice Roll]

The 3.31s won’t have the EcoBoost downshifting often on the highway unladen so I maintain your MPG will be better on the highway. My 5.4 Triton with 3.73s runs up the I-190 bridges (steep) every day in 6th and never has to downshift from final gear to maintain 65. I’d imagine an EcoBoost with 3.31s won’t need to either. Very few unladen situations on the highway have you downshifting unless you have a trailer in tow.

since mine with 3.73s will catch a gear on some hills or mild passing, there is going to be some with the higher gears. Certainly was when I test drove one. It’s subtle and you might not notice if you don’t happen to see the indicator on the dash change

 

[xrcsl]

I think the actual performance of the 3.31 and 3.73 are probably too similar to notice with a 10-speed automatic. My 2019 Max 2WD 3.31 will do 0-60 in a hair over 6-seconds and it is 100% stock. It also doesn't shift out of 10th on the highway unless I put my foot down to pass, which is what it should do.

I am sure that if you took two identical trucks other than their final-drive, the lower (numerically) truck would accelerate slightly slower and get slightly better fuel economy. But they are so close and are both running 10-speed transmissions, that I doubt the real-world performance is going to be very different.

 

[Plati]

I think the actual performance of the 3.31 and 3.73 are probably too similar to notice with a 10-speed automatic. My 2019 Max 2WD 3.31 will do 0-60 in a hair over 6-seconds and it is 100% stock. It also doesn't shift out of 10th on the highway unless I put my foot down to pass, which is what it should do.

I am sure that if you took two identical trucks other than their final-drive, the lower (numerically) truck would accelerate slightly slower and get slightly better fuel economy. But they are so close and are both running 10-speed transmissions, that I doubt the real-world performance is going to be very different.

Oh no no no. There are people on this Forum that have incredible sensitive butt dyno's. They can tell the difference between 2WD & AWD, 91 & 93 octane, diff gearing, whether or not A/C is on, tire treads, you name it - they can tell!!

 

[Deadman]

I think the actual performance of the 3.31 and 3.73 are probably too similar to notice with a 10-speed automatic. My 2019 Max 2WD 3.31 will do 0-60 in a hair over 6-seconds and it is 100% stock. It also doesn't shift out of 10th on the highway unless I put my foot down to pass, which is what it should do.

I am sure that if you took two identical trucks other than their final-drive, the lower (numerically) truck would accelerate slightly slower and get slightly better fuel economy. But they are so close and are both running 10-speed transmissions, that I doubt the real-world performance is going to be very different.

I test drove a 3.31 and it felt lethargic compared to a 3.73.