Corpusfishing.com

[TXHill]

I know there may be some people that take offense to this because it's not fishing related but please bare with me. 2 and a half years ago I booked a trip with Capt. Billy Sandifer down PINS and I was hooked on surf fishing within the first 30 minutes. My son and I now spend as much time together down there as possible. I have followed the sight for years now and know there are several people that would be able to give me some insight into something.
I drive a 2008 F150 FX4 5.4L. It has a 6" lift and 35" tires. I am running with the stock 3.73 gears. I'm looking to go to a set of 4.10 gears. Right now I get 12 mpg and not much in the way of overdrive. Would it improve either one? I'm also wondering, since I do spend some quality time in 4x4 on the beach (taught to run not sit on the beach by the man), if I'm at risk of tearing up my tranny?
Any info is appreciated, thanks to all!!

[shawn]

4.10's on 35's is too high. to get the correct gear ratio for your new tire size take your factory gear ratio multiply that by your desired tire size then divid that by your factory tire size then go to your next lowest ratio

i'm regearing my jeep so this is a good example

desired tire size= 35
stock ratio= 3.55
stock tire size= 27

3.55 X 35 = 124.25
124.25 / 27 = 4.60

4.60 will get you back to stock specs including mpg but it isn't an available ratio. 4.56 would put you a bit high but it won't hurt you. 4.88's is generally what a crawler would go to because of the extra low end available and it won't hurt your highway speed/mileage

[Bluffer]

Get a power commander tuner for that rig, can reset odometer correct & add some HP to the motor. Go with a K&N filter to.
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[Puretexn]

Gear ratio / tire size chart

http://www.4lo.com/calc/geartable.htm

PT

[Big John]

Great chart, and it explains why I get better highway mileage with 265/70/16's over 245's.
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[Mark]

The fuel economy will most likely get worse with lower gears.

[TXHill]

Thanks for all the info!! The chart is awesome!
Leaning towards the 4.56 gears. Just wondering what it will do to my milage? I think Mark is correct in saying my mpg will go down.

[bk005]

All the calcs are good, but make sure you actually measure your tire, if your running 315's or 375's they dont necesairly match up. and you might be suprised if you actually measure what you got.

I would go 4.11's. Just a guess but 4.11's will probably get you back to your original powerband, overdrive will work better, and you wont be kicking out on overpasses all the time.

On your tranny with 35's and 3.73's Id watch your tranny temp on the beach.

[looking]

Also don't forget you have to do the front and rear gears. 4x4's can definitely get expensive.

[TXHill]

You're right bk005. Tires are 35/12.5/17 but measure exactly 34".
I put on a tranny cooler as soon as I got the truck because I was concerned about it.
Looking, thanks for the heads up on doing the front end too. I hadn't thought of that.
Anyone know what would happen to my gas milage if I go to the 4.11 or 4.56 gears? Guy at the shop says it would stay the same but my guess is it will go down.
Thanks for all the info!!!!

[robul]

if your thinking of a computer tune Id stay away from the handhelds and get a custom tune. You will get much better fuel milage , driveablity , and power. Since your up in bulverde I would talk to Corey Henderson @ Henderson Performance in new braunsfel.

[BaitBoy]

4.11 is to 20 mpg as 4.56 is to 18 mpg. The higher the gear ratio the lower the mileage. All depends on what youy are looking to get out of it. Using the numerous calculators available on the net, you can find that a larger tire diameter will get better gas mileage, assuming the gear ratio and your engineHP/torque can handle it. Going to a lower gear ratio, as in from 4.11 to 4.56, and then increasing tire diameter could keep your mileage the same, but if the torque available in the engine can't turn the tires efficiently, that advantage could quickly turn into a disavantage if you are significantly under powered.

[TXHill]

I have the stock 3.73 gears with 35" tires and get 12.8 mpg.
I've spoken with several people and some tell me it will improve my gas milage and some say it will kill it if I go to the 4.56 gears.
From what I've read, it seems like my milage would go down.

[1bgsub]

3.73 gears and 35’s with overdrive is not a good combination. I bet when your running down the highway your transmission is shifting in and out of overdrive constantly. I think you would be better off running 4.56 gears with the 35’s so your tranny can stay in overdrive and with that you should improve your gas mileage. Your performance should also improve with the lower gears because it put your engine back into its happy place.

later
Trey

[Mark]

In my experience, whenever you go to larger tires, the mpg get worse even though the effect is as if you raised the gears but by increasing the tire size, you increase wind resistance. Since most larger tires usually have a more aggressive tread pattern and are often wider, you also increased road resistance. Big tires + low gearing = poor mileage but hey, it's a truck. If you want good gas mileage, buy a car.