i have a 2005 fx4, just bumped up the tire size from 275/65/18 to 295/70/18. anyone have a prefference on gear ratio to run. running the stock 3.55 but thought about bumping up to 4.10s. am i wasting my money or is this a wise move.

 

i would say for that small of a tire size increase, its a waste of money, you will send 1500 approx for gear change, since you would have to do both axles

 

This is a 6.37% increase in overall diameter, not to mention a little additional rotational weight too. A 4.10 set will get you what you need, if you are wanting to spend the coin on a gear change.
For a lot less (about $400) you could contact Mike Butler @ 5 Star Tuning and he could set you up with a custom tune that will accommodate for the increased size and change the shift strategy of the trans. It might be the better, obviously more cost effective, option of the two.

 

You're wasting your money. Unless you tow often, and heavy with your truck, don't worry. I wouldn't go larger without a gear change though.

 

I have to agree with Chandler, the tuner would be your best bet

 

Are you sure you have the 3.55 gears? I'm not being a smart *** but I have a 2004 F150 FX4 and it has 3.73 gears (stock)