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Thoughts on F-150 Axle Ratios

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You don’t have to run it dry, just record the miles driven and number of gallons to bring back to full and do the math, miles/gallons. You are not relying on the vehicle computer system to do the figuring.
You then introduce statistically significant variability in the fuel addition process compared to the sample size of the test/run.
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BlackKnight21

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Does anyone have an opinion on what the best axle ratio is for the 21’ F-150? (3.15, 3.31, 3.55, and 3.73)

Is there any discernible difference between the 3.31 and the 3.55?

Looks like the 3.31 comes with the FX4 package, and the 3.55 come with the Max Tow package.
The 3.73 came with my Lariat Sport FX4 Max Tow Package.
 

daemonic3

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You don’t have to run it dry, just record the miles driven and number of gallons to bring back to full and do the math, miles/gallons. You are not relying on the vehicle computer system to do the figuring.
LMAO duh I'm an idiot. I just forget because I hate putting gas in until it is almost empty, otherwise I feel like I'm wasting time doing extra trips!

I joined Fuelly so I'm gonna be entering my data there and seeing what that gets over time. Multiple tanks should remove error due to differences in pumps topping off any individual tank fillup. (I'm always using random stations, rarely same one repeatedly)
 

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Coolrain

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Since the F-150 does have a 10 speed transmission I would prefer a more agressive gearing(3.73:1). I think there should be an option for an even more agressive gearing with the 3.3 something like a 4.10:1.
Why the 4.10? I’m going with the Tremor and it’s one of the options
 

Mathmatic

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Why the 4.10? I’m going with the Tremor and it’s one of the options
Well I was talking about the 3.3 which don’t have the 4.10:1 option and definitely should as it is weak in the torque department.
 

RidingHighNCO

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It all depends what you use your truck for. The differential gearing multiplies torque and changes the rotational speeds and directions. A high numerical ratio like 3.73 or 4.11 (called a lower ratio, low gearing, or short gears) multiplies the engine's torque more than a lower numerical ratio like 3.31 (called a higher ratio, high gearing, or tall gearing).

So more torque is better, so what is the tradeoff? Engine RPM and fuel mileage. Those 3.73 or 4.11 gears will require the engine to turn much higher RPM for a given vehicle road speed than the 3.31 gear set will. So at 70 mph on the highway you might be turning 2800 RPM with that 3.73 versus 2200 RPM with the 3.31 gears. And with increased engine RPM comes increased fuel burn, so worse fuel mileage. Engine and drivetrain wear may also increase with those higher sustained engine speeds, but that would be hard to prove.

There is no one size fits all gear ratio. The 3.55 is the middle of the pack, and is probably a reasonable compromise, but Ford's engineers have chosen which ratios you can get with which engine, and have specified their towing and payload ratings based on those drivetrain combinations.

Match what you plan to use the truck for with those ratings, and you'll have the gear ratio the engineers believe is best.

Personally, I wish I could have gotten the 3.55 with the PB 4x4, but that combination forces the 3.73 ratio. I know I will not be towing very often, so I'd rather trade a little towing grunt for better fule mileage,. But Ford was designing to a max trailer rating so they decided I cannot have a 3.55 with that truck because it's too heavy, and they think it needs more torque multiplication.
In my opinion Ford has put the combos together pretty well which is based on towing, mass and payload but tires make a huge difference as well. I would have liked to have gotten the 373’s but with all my other options the 355 was my closest option. my truck is coming with 265/70 R18‘s and most likely will not tow anything more than a couple of motorcycles and double I’ll ever go bigger than 33 or 35’s. My thought is I’ll take advantage Of the fuel economy opportunity now and if I ever pull the trigger on a travel travel, just have a new ring & piñon thrown into the deal
 

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Feb 2 Order: 22 Lariat 500A/3.5 EB/FX4/Max Tow/+

ARegularJoe

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Feb 2 Order: 22 Lariat 500A/3.5 EB/FX4/Max Tow/+
Re the front dif. Does Ford March the gear ratios front to.back?
 

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1. I don't get how large pickup trucks and concern over fuel economy go together, but that's just my opinion and a discussion for a different thread ;)

2. Some math (your job to convert to those archaic mpg thingies :ROFLMAO:)
F-150 Revs @ 110km/h
Gear ratios:
14.696
22.985
32.146
41.769
51.520
61.275
71.000
80.854
90.689
100.636
Final drive ratio: 3.73
Tyre Size: 275/60R20 OWL all-terrain
Distance in km for 1 wheel rotation: (838mm x pi)/1,000,000 = .00263265km
Wheel rotations in 110km = 110/.00263265 = 41,782.92
Wheel rotations at 110km/h for 1 min = 41,782.92/60 = 696.38
Driveshaft RPM = 696.38 x 3.73 = 2,597.50
Engine RPM in 10th gear = 2597.50 x .636 = 1652.01 RPM

1652 rpm isn't a lot; I've ordered a KR with max tow 5.0 so it's 3.73, and I can't wait :)
 

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Since the F-150 does have a 10 speed transmission I would prefer a more agressive gearing(3.73:1). I think there should be an option for an even more agressive gearing with the 3.3 something like a 4.10:1.
Plus the 3.73 gives the 9.75 rear over the 8.8. The "9 in" is a stronger unit, bigger axles, etc.

Even if not "really" needed, the stronger rear end is a good idea.

With the 10 speed transmission, the MPG hit really isnt that much.
 

Mtnman1

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I also have the 3.31 gearing in the new truck. (5.0)
with the low gearing of the trans, I am pretty confident this truck will drag most anything I will ever drag with it up to 10-11,000.
Unladen it is plenty responsive and has no trouble moving out.
since most all of my usage is rural/empty, I really don’t have a regular need for shorter rear gears.
It might struggle a bit at Cruise hauling a heavy load, but I am not adverse to winding it up a bit to keep on going.
My old 79 Chev has a 454/4spd and .3.08 rear.
never had a real issue with that thing even pulling grades, I would wind it up tho and watch the tach and fuel gauge try to meet in the middle.
If I have to stay out of the overdrives or even 7 or 6 to get the job done, so be it. For as little time that mine will be dragging stuff, not worth it in the long run for the fuel mileage.
if it goes below 10mpg while actually workin, I’m certainly not gonna get uptight about it.
Ratio is just 1 aspect. If i expected to drag anything, i would want the 9.75, stronger gears, bigger axles, etc.

And comparing a 4 spd with .308 really isnt relevant to the 10 speed with 3.73 or 3.31.
 

Bryan Simon

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Ratio is just 1 aspect. If i expected to drag anything, i would want the 9.75, stronger gears, bigger axles, etc.

And comparing a 4 spd with .308 really isnt relevant to the 10 speed with 3.73 or 3.31.
granted, 4spd to 10spd is “apples & Raisens”

20, 30, 40 yrs ago the tall read ends and no OD was the norm.
Most will not be towing a load of any significance in any OD gear.
The new 10spd has three gears between the old 4-spd 3-4. Much better for getting an optimum power/torque zone.
The old 4spd was used generally as a 3spd (2,3,4).
I never really had issues with this.
My 98 K1500 has 3.73 with a 5spd
Tows just fine ( not using 5th with a load).
Doesnt have the “grunt” of the 454, but gets it done.

Newer trucks are better suited for hauling crap safely with less concerns over capability. But, I can also see how this can lead to overconfidence.
 

RichW

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New guy here , just took delivery of the Limited 150 3.5 EB 4wd with the MANDATORY 3.73 gears. Traded a 2019 Limited that had the 450 hp twin turbo. The EB is quicker off the line , even though I didn’t think that was possible , less hp is faster , obviously way more torque and lower gear ratio . Although I’m not 18 anymore , it was impressive. However, if you go 3.73 gears you better find peace going 65 mph or less on the highway if you want 20mpg. I could sail down the highway in the 2019 at about 75mph a got 23-24 easy. These are Imperial gallons btw, they should go farther. Unfortunately, those days are over. At 70 mph ( still slow in my opinion) you can not maintain 20 mpg. AND keeping away from cruise control the entire time. 24 mpg average is absolute pure bullshit or else you are going so slow you’ll need a tail gunner . If you want mpg and don’t pull heavy loads very often , stay away from 3.73 gears , big big mistake. I have had to drive over 2500 miles in the last 2 weeks , all highway and have been watching carefully the entire time the last trip was exactly 335 miles and I really stayed focused and got 22.3 mpg at an average speed of 62 mph no cruise control and tons very bad thoughts about hills. . One more thing, the transmission will not let go of the 9 th gear until your rpm’s are up into 1.7 nearly 60 mph and no matter how featherlight you are on the gas , this kills the mileage every time . The only solution is DON’T slow down . ( not good) Please tell me there is a fix for that out there other than yelling out loud at the trany in the middle of my wife telling me something important , mercy , really nice ride though ( also if you try Blue cruise , do not have your wife in the passenger seat , just don’t)
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