SteveLord

There was an FX4 option for 4.10 gears in the 09-14 gen. At least on Ford's website. Guarantee its one of the rarest configs anyone would have though.

marshallr

Generally speaking for most of us there is no downside to going with lower gears. Ford is trying to meet CAFE fuel mileage standards. On paper they can show an additional 1 mpg with higher gears. Which is huge for them as many trucks as they sell. And might make a difference in fuel costs for a company with a fleet of 50-100 trucks.

For an individual the lower gears mean more power, and realistically less than 1 mpg in fuel usage. You'll never notice.

With the 3.5 EB you have enough power that the 3.31's would be acceptable. I'd not touch them with the 5.0 nor 2.7. Forget about 3.15's.

My 5.0 has 3.55's and I find them acceptable. I'd have rather had 3.73's but never found a truck with them that I'd consider buying.

AZ_HighCountry_F150

3.55 or 3.73. My previous experience with 3.31 was not good. The 3.55 in the current truck with the bigger tires is more than adequate for the job including towing.

SummitSitter

The 3.55 comes with a Non-Limited Slip Axle Ratio. There is an optional 3.55 Electronic Locking Axle Ratio. Between the two types, what is the difference and what if recommended?

Tom_with_a_Truck

A limited slip has a set of clutches that limit the amount of rotation difference between the two wheels. If one wheel is on ice, it will tend to spin, but the clutches will transfer some power to the other wheel. It's a limited amount of power because the clutch system has to allow for different rotation speed when you go around a corner. A locking differential is different. It locks the two wheels together, so that neither one can rotate faster than the other.

The locking differential is superior for ultimate traction, but it wouldn't work well if you drove around corners because when you turn, the outside wheel has to turn faster than the inside wheel. The electronic locking differential allows you to lock it when you need it, but leave it unlocked when you don't. Best of both worlds - normal driving, and traction-intense situations.

Edit - I need to read better. A non-limited slip differential is an open differential. If one wheel is on ice, it will spin freely while the other does nothing to help. Locking the differential will force the two wheels to operate in tandem. If one wheel has traction, it will move the vehicle regardless of where the other wheel is.

ScubaKen

I had 3.55's in mine, but after a wheel and tire change, I then swapped them out for 4.11's, very happy with this change.

2015rubyFX4

Go with the 3.55's e locker. It will get it into the boost quicker..

BTW I have a 2015 F350 with the 6.2 gasser and 4.30 gears. They are sweet

SummitSitter

Sounds good. I was leaning towards the 3.55’s. So I guess you are saying that it will get the turbos to kick in quicker. I’m still debating whether to get the 2.7 or 3.5 EB. I’m not planning on towing and from what I see they both get about the same gas mileage. With the 3.5 you are getting 50 more HP, but you paying extra money for that engine. I haven’t heard any complaints about the 2.7. Is there a definite difference in acceleration with the 3.5 over the 2.7? Any other advantage with the 3.5 other than towing?

chimmike

don't listen to anyone who mentions lag with regards to the 2.7 or 3.5 ecoboosts. There is no lag. none. So don't worry about lag with regards to gearing, no matter what gears you have.

btw, you're getting 50 more hp and 70ft-lbs more torque, but you're also getting more displacement, which for towing, means it doesn't have to work as hard towing the same load as the 2.7.

SummitSitter

I’m not worried about lag between the two engines. Just trying to figure out what gearing is best. I’m most likely going to do a 2” leveling or possibly a 4” lift. Most likely won’t be doing any heavy towing. If I won’t see a major difference in MPG’s, I might just go with the 3.5 EB for the extra HP and the 3.55 gearing...