ok i don't want to hear any B.S. about the faster acceleration making up for the lost MPGs. i just want to know about how much MPGs i may lose if i switch it. thank you.

 

It depends on your driving style, city vs highway driving, and tire size. If you have slightly larger tires and live and drive in the city it might go up.

Lots of different factors.

 

im about to do the same swap.. my truck already sucks at a best of 15 mpg how much worse could it get..

 

just an average driving style, during the week, also i mainly just wanted to know what other people lost, when they switched, if i had to guess i would think maybe 1-2MPGs, maybe 3 cause i'd rather over estimate then be under.

 

If you keep your foot out of the firewall, you probably won't lose any mileage. Make sure you adjust the speedo/odo for the different gears.

 

The rpm change for any gear mod is 300 rpm for each .25 gear ratio change- in summary you are only looking at about 300 more rpm.

 

it mostly depends on whether you drive city or highway. if you drive mostly city then there's a good chance you'll see an increase.

highway it may drop 1 or 2 mpg.

 

well i work at UPS and start at 3 in the morning, it's all city driving , but at 3:00AM so, kind of an average and i figured that city MPGs would go up, also i probably should have mentioned this sooner but this stock wheels and suspension, so this is for more of a street/strip application. and i have also been thinking maybe, 373s but 410s are $20 cheaper. thanks for all of your help so far.

 

I gained mpg around town, stayed the same on the highway.

 

What he said^^^. I'm assuming you guys that suspect a loss have never actually done it?? I GAINED 1-2 everywhere, and have seen a best of 3 mpg increase. There are ZERO downsides from doing a gear change.

3.55 to 3.73 is NOT worth the cost or the effort for such a small change in ratio. You will not regret 4.10's. It completely transformed my truck across the board.

 

Hi

I bought a used 2005 fx4 (50K miles) with 6 inch lift and it has 325/60/18 tires. I also added Custom 87 tunes (performance, tow, MPG) from VMP but am just not happy with the pick up or mileage in the truck.

I live in Austin, tx and am mainly city driving up and down hills in NW austin so I am wondering if a gear change from 3.73LS to 4.10 would help me?

Thoughts?

 

In your case I would go 4.56's....

I went 4.11's and I have smaller then factory diameter tires. I wish 4.30's were made for our 9.75 rear ends.

 

It's amazing all this mis-information on the internet from people who have not done it to their truck.

People to this day still don't beleive my truck was getting 21-22mpg before I installed my blower. Which on the highway I see anywhere from 17-19mpg. Depends on how fast I drive(70-85mph).

 

I think these trucks should come with 4.10's out of the factory. They are the heaviest trucks out there but still have the same gears as the light weight 97-03's. Look at the Tundra's they come with 4.30's from the factory, and they perform really well compared to a comparable F150 with 3.55/3.73 gear ratio.

 

They don't come with 4.10's because of the EPA gas mileage - which does not necessarily correspond with real world gas mileage.