RedsRock302

Completely my fault, I updated it.

blue5.0

I went to 4.10's from 3.31's and it has been a wonderful experience. My tires are 275/55/20

M0RRIS

Thank you, I was certain where I sat at 70, I just wanted to make sure

FXtreme5.0

iTrader: (1)

I'd ask about your MPG's but I can tell by what u keep doing to your truck, that u have no idea
Think u & I probably drive in the same manner, which is why I honestly don't know how well/bad my truck does, so I ask people who watch

FXtreme5.0

iTrader: (1)

Thank u everyone for your responses & experiences, I love this Forum already
Honestly I don't tow much with this truck & I am not comfortable about jumping 3 Gear Ratios.
In my mind 2 seems perfect, should be enough to make a difference, without making such a difference that I'd regret it.

Austin13FX4

I'm new to the forum, and this was a question I researched for a long time. I was on factory tire size in my fx4 with a 5.0 and 3.31 gears. I leveled it and put a 35/12.50-20 M/T all the way around, and my gas mileage dropped ridiculously. I was averaging 18.5-19 highway and a solid 15.8-16.2 in town on stock size at's. I dropped to 14.2 as my best on highway and 10.5-11.5 in town. Towing was harder as well, the power loss resulted in more downshifting and I lost the ability to run 6th gear at all with my 9k pound boat and trailer. I researched a gear swap a long while and couldn't really find many that had swapped in 4.10's, most had 4.56 or 4.88's.

So, I bit the bullet, swapped both front and rear diffs from 3.31 to 4.10's, and I will never look back. I added a programmer as well to correct the speedo. Mileage is now 17.5-18 highway, and 15-15.5 city. Towing is effortless, better than factory in fact. I rarely drop lower than 5th gear climbing a grade while towing, and I still average about 13mpg with my boat and trailer combo. My honest opinion, with having done this myself, is if you are planning on running a 33" tire or bigger, 4.10 is the way to go. The off the line acceleration is crazy, and the fact that unloaded it goes into 6th gear and never comes out rolling down the highway makes it feel so much more powerful.

Good luck in whichever way you decide, this was just my 2 cents!

SteveLord

Austin-

Did you use stock programmer tunes? Or get a custom? Should always do the latter. Especially with a gear change.

jp360cj

I think the general perception (granted it's often true) is that lower gears mean lower MPG's. As your truck proves, that's not always the case. Sounds like you don't regret it a bit.

Also, what year is your truck? I thought all FX4's got at least 3.55s.

Austin13FX4

FXtreme5.0

iTrader: (1)

Update... On March 3rd, we ended up signing on a new home! The wife & I have been longing to "build" a new home for approximately 10 years & acting serious for nearly 2 years now. Well, it's finally happening & we should be moving sometime in July!
Of course, the gear swap was put on the backburner. I'll get to it when my checkbook cools off