gear ratio swap

[ididieseler]

I'm currently running 3.50 gears with 35 12.5 15 tires, i want to get a little more power, i dont really want to keep having to downshift for hills as much as i do. how much hp would i gain if i swapped in 4.10 gears? also, how much would my gas mileage suffer, the truck is a 1978 f150, i have a 7.3 with a banks sidewinder turbo and a zf5 speed trans, 3.50 gears and 35 inch tires, im currently getting about 16 running winter blend fuel, in minnesota so its subzero about half the time right now lol. how much gas mileage might i lose going to lower gears?

 

[fordf350man]

you wouldn't gain hp by changing gears, and it will affect your fuel mileage though definitely, i would look for something in between like a 3.73 ratio, then you kind of get the best of both worlds, 4.10 will drop your fuel mileage more than what i think you want it to,

 

[ididieseler]

its not gonna affect the motor, but it should give me more hp at the rear wheels.

 

[fordf350man]

no, all its going to do is change the speed at witch you reach your maximum horsepower and torque, the engine will put out what it can and there will be some lost in the transmission, what you are going to feel is the peak horsepower and torque at a lower speed, now what do you use the truck for? is this a daily driver or a play truck? you have 35s on it so i am assuming you like to go off road, me to who doesn't? anyway if its more of a play truck then i would say go for the 4.10s, but if you drive it daily and want to play but want some fuel mileage i would say then go in between the 3.50 and 4.10, that will give you the best of both worlds, you have the extra low end power for playing or towing and and still drive it daily and not kill your pocket with fuel cost, i cant say for a diesel but i had a 5.8l f250 with a zf 5 speed and 35s on it and i got around 6 to 7 mpg, now i also had some steel bumpers on it and im sure the diesel would be better but probably not by a whole bunch, all really depends on what you do with it to make a decision

 

[jonathan]

I have 410 in my truck and I get 17 mpg highway

 

[fordf350man]

that's incredible, i have 3.55 in my truck with 35s and i get less than 15 on the highway, how are you getting that kind of fuel mileage with 4.10s, please tell me

 

[FarmerFrank]

the bronco had 31x10.5x15 tires and 3:55 gears, when I lifted it and put 35x12.5x16.5 tires on I also swapped out axles for 4:10's. it ran exactly the same and the speedo was off the same amount.

 

[88fordidi]

yeah I get in the 17-18 range with 4.10s; if I could keep my foot out of it probably 20, but that just isn't going to happen. 4.10s with 36s is equal to stock tires and in the neighborhood of 3.10 axles.

 

[fordf350man]

he already has 35 inch tires on it, and is getting 16, so if he went to 4.10s then he might gain city mileage but would lose on highway

 

[88fordidi]

honestly depending on his horsepower his milage might go up, lower gears can increase milage in a gasser depending on the build lol

 

[TWeatherford]

I got 17 highway only with a SRW F-350 cclb with 4.10s, zf5, and 4x4.

 

[FORDF250HDXLT]

I'm currently running 3.50 gears with 35 12.5 15 tires, i want to get a little more power, i dont really want to keep having to downshift for hills as much as i do. how much hp would i gain if i swapped in 4.10 gears? also, how much would my gas mileage suffer, the truck is a 1978 f150, i have a 7.3 with a banks sidewinder turbo and a zf5 speed trans, 3.50 gears and 35 inch tires, im currently getting about 16 running winter blend fuel, in minnesota so its subzero about half the time right now lol. how much gas mileage might i lose going to lower gears?

you don't lift 'em and run 35" mudders if fuel economy is of a concern.
the ring and pinion for your truck should be a set of 4.56 minimum and 4.88 if you wanted some real mudding power for some fun in the pits.
lower gears don't help hp.they multiply torque.

 

[icanfixall]

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This is what my engine rpm and mph are and I got 18.9 over a 2200 miles unloaded trip home from the 2009 rally in Ky. Thats with a Gear Vendors and E4OD so double overdrive. Gears are 3.55... In double overdrive my final gear ratio is 1.96...

 

[ironworker40]

RUN IT DOWN THE ROAD IN FOURTH. THAT WILL BE THE MILEAGE YOU WILL GET WITH 4.10'S GIVE OR TAKE. 4th is 1to1. just like your truck was when it cam out of the factory in high gear. you can drive it forever and not put in 5th. won't hurt a thing

 

[bobracing]

Best gear calculator I've found.
http://www.grimmjeeper.com/gears.html

No trans was mentioned so mpg gets a little fuzzy.
With no OD, might loose a little on the hwy but gain some in town.
With OD, might actually get better, the gears might put the Rpms in a sweeter powerband using less fuel at a little higher RPM.
Pretty sure your butt dyno would notice the useable power.