Ifallsguy

I've been considering changing out the rear end of my '16 Lariat 5.0 RWD from 3.55 to 3.31. Anyone ever try this? I know Forscan would let me change the computer for the gearing change. I do a fair amount of interstate driving and would like to see an improvement in MPG.

I'm wondering if anyone has changed out their 3.31 electronic locker and is looking to get it out of their garage.

Georges93LX

iTrader: (1)

For the cost of changing gears it will take forever to realize the savings. If you were going from 3.73s it wouldn't hurt quite as long. There's just not enough difference for you to make the change. My 2014 came equipped with the 5.0 and 3.31 and I get 15mpg city and 19-20 hwy. Even the new 10 speed gets crappy mileage. They are called trucks. You can't use truck and good gas mileage in the same sentence. Just my $.02.

slowpony46

It’s not that much difference, I don’t think you’d see enough change in mileage to be worth the effort, cost, and performance loss.

BadBoy4fun_wa

Mine seems to like 70 way more than 80. Probably best savings on v8 gas is slowing down on highway ;-). I bet you never thought of that :-)~~~~

caperJ

Sold 2015 3.55 purchased 18 3.31, would never do it again. No difference in mileage and 3.31 hunts on the new 10 speed. I can see Ford putting this in a 2wd but not 4wd. Hate the 3.31 gears best of nothing.

caperJ

2013 3.73 was my favorite gear and since then I have seen no improvement in MPG.

Z7What

Lets do the math here $700ish for Gears & Install Kit PLUS labor. Lets say labor is $300 but honestly it will probably be closer to $500 but we will use $300 to make things simple. So your grand total for swapping out the gears to gain MPG is $1000

You never mentioned what milage your getting now but ill guess 17, lets say you gain 2MPG and its puts you at 19.

If you have a 26 gallon tank thats a extra 52 miles more out of a tank. So at your now 19MPG your saving 2.73 gallons per tank.
If you have a 36 gallon tank thats a extra 72 miles more out of a tank. So at your now 19MPG your saving 3.79 gallons per tank.

Lets say gas where you live is $3.00/gal

For your 26 gallon tank your saving $8.19 per fill up assuming your COMPLETELY empty when filling up.
For your 36 gallon tank your saving $11.37 per fill up assuming your COMPLETELY empty when filling up.

$1000(Install of gears) / $8.19 (26Gal Tank Fuel/Savings Per Tank) = 122.1 COMPLETE Fill Ups BEFORE YOU BREAK EVEN.
$1000(Install of gears) / $11.37 (36Gal Tank Fuel/Savings Per Tank) = 87.96 COMPLETE Fill Ups BEFORE YOU BREAK EVEN.

So basically its will take you 1.5-3years to BREAK EVEN if you fill up once a week. Im sure it will be alot easier for you to find someone with 3.31 gears that would swap entire rearends with you. That way it would be more cost effective.

This math doesnt go for just gear installs, it goes for anybody wanting to modify to save MPG. In the end, its really not worth it. I always say modify for performance and performance only, if you gain MPG with those performance mods then it makes it that much better but most of the time its not cost effective to mod just for MPG only.



And to to mention like it was said above you will LOSE performance not gain performance.

Wayne

Fx4gary

I agree completely, my 13 had 5.0 and 3:73's. Maybe .5 to 1 mpg difference in the new truck, but it's also 700 lb lighter. The 5.0 is sluggish off the line with the 3:31's. I wouldn't spend the money on the rear gear change, you won't be happy with the performance and it'll take forever to realize any gas savings.

Thugzy

Did you get your 2018 checked yet?

My 2018 3.31 is far superior to my 2015 3.73. Performance overall and heavy towing. I have zero hunting with my 10 speed.....

chimmike

disagree about the 10speed hunting with 3.31s. 13k miles on '17 3.5 EB with 10sp auto. It does awesome on the highway and holds 10sp without issue.

FYI the 10sp with 3.31s is similar to the 6sp auto with 3.73s through most gears.