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3.73 vs 4.11
- Thread starter Antonio_kheir
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jorligan
Member
There is a reply on f150 forum where they went with 4.11 gears and they report better mileage and performance as it didn't need to downshift as often. I have the 5.0 with Whipple and am getting 4.11 gears, 35x12.5x20 on Fuel wheels, should be getting my truck back in a couple of weeks and can let you know.
Antonio_kheir
Member
- Thread starter
- #20
That would be great!
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Antonio_kheir
Member
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- #21
So I've done some math.... Could totally be wrong as I made an assumption to help with simplification.
These calculations were all performed using a 33" tire from factory:
3.31 -> 3.73 = +12.68%
3.31 -> 4.11 = +24.16%
3.73 -> 4.11 = +10.18%
these numbers just reflect the percentage increase in gear reduction from my 3.31s
Next, moving from a 33" tire to a 35" tire is an increase of 6.06% in tire diameter
the stock hankooks weigh approximately 42lbs per tire, 168lbs total which is ~ 1,411 lbs of rotational mass. A 295/65/20 ridge grappler weighs approximately 70 lbs per tire, 280 lbs total which is ~ 2352 lbs of rotational mass. that about a 66% increase in rotational mass!
So knowing all this, if going from a 33" to a 35" is a 6% increase in tire size, I made an assumption for simplification that it would also equal a 6% decrease in performance. As said before, if going from a 3.31 to a 3.73 = an increase of 12.68%, then 12.68% - 6.06% = net gain of 6.62% in performance. 3.31 to 4.11 would also have a net increase of 18.1% in performance. These calculations did not take into account the rotational mass increase of the tires (don't really know how to do that).
Looking at these rough calculations, this means that even a truck with 3.31s and 33s would perform worse than a truck with 3.73s and 35s? or is this completely wrong?
Hopefully this might help someone if these numbers are somewhat accurate. And if someone is more knowledgeable on this stuff, please chime in!
These calculations were all performed using a 33" tire from factory:
3.31 -> 3.73 = +12.68%
3.31 -> 4.11 = +24.16%
3.73 -> 4.11 = +10.18%
these numbers just reflect the percentage increase in gear reduction from my 3.31s
Next, moving from a 33" tire to a 35" tire is an increase of 6.06% in tire diameter
the stock hankooks weigh approximately 42lbs per tire, 168lbs total which is ~ 1,411 lbs of rotational mass. A 295/65/20 ridge grappler weighs approximately 70 lbs per tire, 280 lbs total which is ~ 2352 lbs of rotational mass. that about a 66% increase in rotational mass!
So knowing all this, if going from a 33" to a 35" is a 6% increase in tire size, I made an assumption for simplification that it would also equal a 6% decrease in performance. As said before, if going from a 3.31 to a 3.73 = an increase of 12.68%, then 12.68% - 6.06% = net gain of 6.62% in performance. 3.31 to 4.11 would also have a net increase of 18.1% in performance. These calculations did not take into account the rotational mass increase of the tires (don't really know how to do that).
Looking at these rough calculations, this means that even a truck with 3.31s and 33s would perform worse than a truck with 3.73s and 35s? or is this completely wrong?
Hopefully this might help someone if these numbers are somewhat accurate. And if someone is more knowledgeable on this stuff, please chime in!
Ranger621
Well-known member
I have a 2022 lariat with the 5.0 and 3:73 gear with 35's I tow a 6000 pound boat with no problem. If you go to 4:11's your milage is going to suffer and you don't need that gearing for daily driving.
ThumperF150
Well-known member
Old thread but my thoughts, please tell me if I am wrong.
Background, I've had a couple of jeeps that I lifted and installed larger tires and re-geared and I have always been glad I did.
I have a 24 RCSB 4X4 ordered. I plan to level and install 35s. Looking at the gear charts, going from the stock 31s and 3.73 gears to 35s with 4.11 gears the RPM difference at 60 mph is only 10-12 RPM. So I am thinking my speedo and shift points will all be the same. Doing my own math, the 35s are about 10% taller than the 31s and the 4.11s are about 10% lower than the 3.73s (rough fuzzy math) but it all kind of makes sense to me.
Background, I've had a couple of jeeps that I lifted and installed larger tires and re-geared and I have always been glad I did.
I have a 24 RCSB 4X4 ordered. I plan to level and install 35s. Looking at the gear charts, going from the stock 31s and 3.73 gears to 35s with 4.11 gears the RPM difference at 60 mph is only 10-12 RPM. So I am thinking my speedo and shift points will all be the same. Doing my own math, the 35s are about 10% taller than the 31s and the 4.11s are about 10% lower than the 3.73s (rough fuzzy math) but it all kind of makes sense to me.
HammaMan
Well-known member
That makes a lot of assumptions. 35s aren't 35" diameter and certainly not 35" rolling diameter. look at the exact tire specs to get the info. My factory tires were 32.9 and I swapped to 34.1 tires which changed the effective gearing from 3.73 to around 3.59 (IIRC). I saw no hit in mileage. The F150 has plenty of power and loads of gears so your jeep experience shouldn't influence you here. A RCSB w/ 3.73s and a 5.0 has plenty of torque to the ground w/out even using 4L. Get the truck and play with it, you'll likely find the 3.73s more than adequate for what you're looking to achieve.
SilverPigeon
Well-known member
I did the following math for my truck's stock tyres. The only assumption made (which turns out to have a minimal affect upon the end result is tyre circumference. I also found it easier to work in metric and converted your situation to metric at the beginning and back to imperial at the end.
The 4.11 final drive certainly overtakes the 35" tyres regarding the effect it has upon cruising rpm, but it is also certain that the new tyres will have some effect upon torque/power. I'm too rusty to do those particular calcs, but with what I've provided here you can slot in any of the variables at least to know rpm at any given speed and gear. First is my truck, second is your situation:
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
(This is so close to actual as to make no difference)
Tyre Size: 35"
Circumference (mm) = pi x 889
Distance (km) for 1 wheel rotation: (pi x 889)/1,000,000 = .00279288km
Wheel rotations in 110km (0.62137119mi) = 110/.00279288 = 39,385.87
Wheel rotations at 110km/h for 1 min. = 39,385.87/60 = 656.43
Driveshaft RPM = 656.43 x 4.11 = 2697.93
Engine RPM in 10th gear = 2697.93 x .636 = 1715.88 RPM @ 68.35mph
The 4.11 final drive certainly overtakes the 35" tyres regarding the effect it has upon cruising rpm, but it is also certain that the new tyres will have some effect upon torque/power. I'm too rusty to do those particular calcs, but with what I've provided here you can slot in any of the variables at least to know rpm at any given speed and gear. First is my truck, second is your situation:
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
(This is so close to actual as to make no difference)
Tyre Size: 35"
Circumference (mm) = pi x 889
Distance (km) for 1 wheel rotation: (pi x 889)/1,000,000 = .00279288km
Wheel rotations in 110km (0.62137119mi) = 110/.00279288 = 39,385.87
Wheel rotations at 110km/h for 1 min. = 39,385.87/60 = 656.43
Driveshaft RPM = 656.43 x 4.11 = 2697.93
Engine RPM in 10th gear = 2697.93 x .636 = 1715.88 RPM @ 68.35mph
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HammaMan
Well-known member
You have to look at a SPECIFIC tire's specs. They're not all the same. Nitto recon grapplers for instance in 35x12.5R20 are 877mm whereas another is (BFG) 876mm, another still is 883mm. Tires are 'about' that size. If someone has a 'tall' version of one and want to see how a gear change and tire will do with another, their calculations can end up skewed. My 34s are 34.1" while some "35's" are 34.4". Would going from 34.1 to 34.4 be a big difference? No. But if I was calculating for 34" on the nose vs 35" it'd start to add up. Rolling diameters differ as well between SL/XL and E rated LTs. When programming the truck for tire size you'd want the actual tire specs to match up pretty close. With my 34" tires the truck still does 0-60 in mid 4 seconds. It still does high 19mpg at 80mph and can get 24mpg around town. I couldn't see the highway mileage maintaining w/ higher ratios given it spends most of its time in 10th.
OIF_Veteran04
Well-known member
I have a 23 regular cab short bed. It have the super 8.8 with 3.31 gears in it now. I'm wanting to go to 3.73.
One of the shops here told me that the whole truck would have to be reprogramed if I do this.
1. Is this true?
2. If it do what needs to be reprogramed?
3. Is the programming able to be done through forscan?
The reason for wanting to change the gears is because I'm adding a whipple in a few months.
One of the shops here told me that the whole truck would have to be reprogramed if I do this.
1. Is this true?
2. If it do what needs to be reprogramed?
3. Is the programming able to be done through forscan?
The reason for wanting to change the gears is because I'm adding a whipple in a few months.
v8440
Well-known member
If the shop used the phrase "the whole truck will need to be reprogrammed" they probably don't know what they're doing. That's not the phrasing someone knowledgeable about it would likely use.
OIF_Veteran04
Well-known member
That was my first thought. But it a highly recommended and reviewed shop.
So they were saying that it would affect so many things like the shifting, the traction control, ABS, and a list of other things.
But I was thinking only the speedometer would have to be recalibrated.
v8440
Well-known member
Well, looked at that way they're right, it will affect those things. I don't think a ton of modules need to be reprogrammed to account for the change, but I'm not sure about that so I'll defer to others more experienced with that part of these trucks.
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