Hi this is my first post on the forum and would like to know about what gear ratio I should be running.

What I want to do is lift my 2011 3.5L Fx4 6 inches (RC with N3 shocks). Which means I want to/will be in the future put on bigger tires. I learned I will need different axle ratio?

I am coming from p275/65/R18's (Kumho Road Venture AT51) to 35X12.50R17 (318/72/17 BFGoodrich Ko2's on NEW RIMS).

From what I gathered my wheel base is 163 inches long. According to the brochure that Ford made back in 2011 the only combo is a 3.73 axle ratio. (first pic with info below it)

When I go to Tiresize's website and use the gearing calculator and put in stock 275/65/18 then put in new tire 318/72/17 with the stock gear ratio of 3.73. I get Effective Gear Ratio of 3.42 and New Ratio Needed 4.07 I can not find any info on what these two ratios mean.

If you say what gearing I need please recommend me a brand so I can look into the brand in more depth. I honestly know zero companies who makes gears.

Any help is much welcomed I am new to the car world as well (1yr of owning the truck/learning cars) and want to learn as much as possible. Also worth noting I am the 2nd owner of this vehicle and It has the towing package.

Thanks,
Jay

I'm 6 feet tall and can lay down in my bed (6.5ft) so I know I don't have the shorter Wheel base (5.5ft bed) so that is why I chose the 163 inch WB unless its something completely different but that is how I figured how it would be.

 

I would go with 4.56:1 ratio differential if going from 3.73 and to 35" tires. 2 steps. If 4wd, gotta do the front also.

 

Along the bottom of your door sticker will be the axle code. It'll be 2-digit alphanumeric, something like B6 or H9. That'll tell you your axle ratio with certainty. With the 6 speed trans. I think 4.10 would be a good choice. The 6 sp. has a low 1st and 2nd, and therefore launches well without having to go as low with the final ratio. If this was a 4 sp. auto in question, I'd recommend 4.56 without hesitation. That's exactly what I put in my '05 with 35's and it's a perfect compromise (everything is a compromise). It launches beautifully, but gives up some effective overdrive as a result. With the 6 speed, it's not an issue.

 

If you already have 3.73 gears, 4.10/4.11 will be a huge waste of cash (Around $2000 give or take). You'd want 4.56 or 2 tiers (as mentioned before) to make it worth it


But then again, since you have the Ecoboost, you might be fine. You'll just be in turbo a lot more than you are now. Best bet is to do your other mods first, get a tune (you would need one with new gears anyway) and see if you still want more. A tune alone will really bring out more power. Best to spend $400ish first on that.

 

You have the 145 base. 163 is the 8' bed. This also is clearly shown on the door sticker.

 

I'd assume the front are the same size as rear? Also thanks for the help.

 

Yes. 4WD means you pay for both front and rear to be upgraded. So essentially double the labor.


Again,
Check your door sticker, snap a pic and post it here or share the info. Then you'll know for sure what you have currently.

 

 

If you have 3.31 or 3.55, this might be what you want. If you have 3.73, skip it all and just see what a tuner will do. I doubt you'll be disappointed.

 

With that engine you'll be fine with 3.73's and those tires. Maybe even 3.55's.