I was just wondering one thing, I was planning on changing my gears from 3.73 to 4.56 soon so my question is if my gas milage will improve/stay the same as a result of this with the change in gears.

 

You should see a slight increase in mileage since you have bigger tires. the different gears should take a bit of load off of the motor when driving around town. A slight increase on the highway only if you drive in real hilly country. Straight, flat roads, not much if any increase.

The biggest difference will be in performance.

 

Theoretically, your mileage will stay so close to the same that you couldn't measure a difference. But most people see a significant change for 2 reasons:

1) they don't recalibrate the speedo/odo after a tire change, so it becomes inaccurate, making it LOOK like economy has changed.
2) because of the change in performance, their driving style changes, causing their fuel consumption to change.

 

Can someone tell me what rear and front ends are on the 2005 F150 FX4? I need to buy gears due to my large tires and I am not sure whats on it. What gear size do you think I need with 35" tires? 4.88 or bigger?

 

If its the same as the 04's the gear ratio should be 3:73. With 35's I would recommend 4:56,4:88 are more for 37's. I'm sure you'll get more input from others incase I might be wrong.