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Swapping in 3.55 or 3.31 Gears into a 4WD

nitrobass24

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So I was reading this thread here about a guy with a 2WD PB and he is getting crazy high MPGs, 30+, at over 70MPH. Im curious is this just due to the gearing being different?

If thats the case what would I lose by going down in gearing?
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dmac

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It’s Additional driveline drag and weight too. Does the 2wd have shorter tires? Maybe the overall ratio isn’t much different then.
This^. Skinnier less diameter tires that are light and low rolling resistance will help way more than gearing. Any level or lift will also hurt. The 2wd's sit lower with smaller lighter tires.

Most 2wds have tires < 32" which can make a 355 or 331 gear ratio more like a 373 on a Platinum 4wd with 20s.
 

dmac

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I think that guy you saw also removed his cats and had an aftermarket tune with high octane fuel. That will make up a lot of the difference. His breathes and drinks way better than us plebeians.
 

HammaMan

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So I was reading this thread here about a guy with a 2WD PB and he is getting crazy high MPGs, 30+, at over 70MPH. Im curious is this just due to the gearing being different?

If thats the case what would I lose by going down in gearing?
3.55 is part of it. His smaller tires increase the ratio a bit though, his lower stance helps out the most. I have 275-65-20s which changed my to-the-ground ratio from 3.73 stock (33" tires) to 3.6 w/ the 34.1" tires. My truck ends up 2" higher than his in the rear and 2.5" higher in the front. The 18" wheels come with smaller tires than the 20" wheels.

My mileage hit is non existent based on my fixed course testing pre-post tire swap. Hugging the ground is the biggest benefit.
 

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Mtnman1

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So I was reading this thread here about a guy with a 2WD PB and he is getting crazy high MPGs, 30+, at over 70MPH. Im curious is this just due to the gearing being different?

If thats the case what would I lose by going down in gearing?
With the 10 sp tranny..hears aint gonna make that much difference.

All highway will get good mpg. Its the stop and go that kills mpg.

My highway mpg takes a dive over 73 mph.
 
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nitrobass24

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3.55 is part of it. His smaller tires increase the ratio a bit though, his lower stance helps out the most. I have 275-65-20s which changed my to-the-ground ratio from 3.73 stock (33" tires) to 3.6 w/ the 34.1" tires. My truck ends up 2" higher than his in the rear and 2.5" higher in the front. The 18" wheels come with smaller tires than the 20" wheels.

My mileage hit is non existent based on my fixed course testing pre-post tire swap. Hugging the ground is the biggest benefit.
Yea I am running the same setup as you. I have the pirellis...not that it makes much of a difference.
On 93octane I see about 27mpg @ 65MPH, 22mpg @ 75MPH. I do about 25k highway miles/year, so if theres something I could do to get into the 30s I could pay myself back relatively quickly.

I've also been considering a reverse level to lower the rear as I have always leveled my trucks, but don't really want to raise the front on this one any more.
 

HammaMan

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Yea I am running the same setup as you. I have the pirellis...not that it makes much of a difference.
On 93octane I see about 27mpg @ 65MPH, 22mpg @ 75MPH. I do about 25k highway miles/year, so if theres something I could do to get into the 30s I could pay myself back relatively quickly.

I've also been considering a reverse level to lower the rear as I have always leveled my trucks, but don't really want to raise the front on this one any more.
So you increased tire size as well? Not sure what removing the rear block would do for you on the aero. Does your airdam work? What tires / size you running precisely? Mine are LT
 
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nitrobass24

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So you increased tire size as well? Not sure what removing the rear block would do for you on the aero. Does your airdam work? What tires / size you running precisely? Mine are LT
Pretty sure my airdam works, but admittedly not sure how I would test that. I never disabled it or anyhting so I havent even considered it wasnt working.

Im running the Pirellie Scorpion all terrain plus. 275/65R20 116H @ 40 PSI. Its an SL tire. 48lbs per corner.
 

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So I was reading this thread here about a guy with a 2WD PB and he is getting crazy high MPGs, 30+, at over 70MPH. Im curious is this just due to the gearing being different?

If thats the case what would I lose by going down in gearing?
He's got a few different things going on as well, different cold air intake, RAM air setup, intercooler. While none of these are a huge increase in MPG all of them added together help quite a bit, then the lack of a transfer case, then the gearing, HT tires are a lot lighter as well. Then he just added a adjustable suspension where he can tune rebound, it's a good setup he has going for sure.
 

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I have 3.31 FX4 on a 2023 EB3.5 ... I drive a about 60% freeway and average 19 to 21/22 ... rarely over 75mph. In Socal, so we have lots of hills and some mountains too. Even with the wind behind me and resetting the computer it would be hard for me to get 26. As mentioned, speed is a key factor, accelerate moderately and just drive easy is the best ... tires too, keeping stock tires w/ 2 or 3 over psi would probably help too. (I have Toyo ATIII - same size as stock, but did take 1 mpg off the top, easy).
 

ks54703

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So I was reading this thread here about a guy with a 2WD PB and he is getting crazy high MPGs, 30+, at over 70MPH. Im curious is this just due to the gearing being different?

If thats the case what would I lose by going down in gearing?
Your Platinum PB is set up like all other 4WD PB's to start out with a 37kw electric motor that utilizes and is optimized through 3.73 gearing. Bottom line when lugging a electric motor it USES more current the usage of more current means less electric miles. 3.31 or 3.55 gearing will hinder more than help on starts and overall electric miles driven.

Tire pressure and type of tires are the first and easiest way to raise fuel mileage. Mine are kept at 38psi on all corners. This gives about 41-42 hot PSI well withing the limits of the tire. Ford sets 35psi as recommended PSI for more than just payload it is also recommends 35 PSI tire pressure for COMFORT!!.

Driving style not going there, lowering lifting the truck not going there either.
 

Rcanning

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I think livernois tune is also making a bigger difference. Can run longer by using more battery power so can stay in electric mode more often
 

HammaMan

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Your Platinum PB is set up like all other 4WD PB's to start out with a 37kw electric motor that utilizes and is optimized through 3.73 gearing.
I've played around with seeing where the power is with the electric motor and have come to the conclusion that the gearing choice from ford is centered around easing the job of the transmission. The 2wd comes with 3.55 as it's a given there's traction limitations in a 2WD truck. 4WD changes that variable. The PB already puts the 10r80 at its torque limit especially as it's always shifting right into peak torque. (furthermore I've got logging showing peak output power of 44kW, just exceeding the 160a fuse rating)

The electric motor will still pull just as hard in 3/4/5 at low RPM. EVs are typically geared around 9:1. The motor used for the PB isn't a typical EV style, they often have smaller diameter rotors whereas the PB's is larger diameter/ flatter, and is geared around more torque at lower RPM than high revving which it can't do as it's coupled to engine RPM.

Ford F-150 Swapping in 3.55 or 3.31 Gears into a 4WD 1712217961408-27


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Ford F-150 Swapping in 3.55 or 3.31 Gears into a 4WD 1712220036298-84
 

Spidergears

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I’ve got 3:31, 3.5, no PB. When I ordered, I figured the transmission would make up for any lower gearing I needed for the most part, so I went with the 3:31 for fuel economy. But, I only get like 13.5 around town and 21 on the hwy.

Here’s something I’ve noticed, at highway speeds it doesn’t take much at all to be in boost. Going up a slight hill, boost, accelerate a smidge, boost. That means more fuel. I have to wonder if shorter gears could actually result in better fuel economy at highway speeds.
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