Question, whats gonna happen to my mileage when I change my gears to 4.10 from 3.73. Right now, I am only getting like 20 mpg on the highway and the truck really feels like it is boggin. I think I am having to use more gas to keep it going lets say at 70 than I did. So, will my mpg go up when I change to 4.10 or go even more down?

 

before you swap, when was the last time you have done a tune up? There are sooo many factors to milage that it is hard to say if it will increase a substantial amount. Are you buying gears? or swaping in a rear end that already has them?

 

You say its bogging? First try and run some BK44G through that puppy. That normally gets my cars up and kickin.

 

Swap in a rear end that already has it. I'm talking to a guy about it.

If I am in a good head wind, it is 4th gear most of the way.

Over winter break, I tuned the truck up. All new plugs, timing belt, timing belt tensioner, water pump, air filter, changed oil, new radiator fluid, cant think of what else.

I was just wondering in general if the mileage should go up or down more.

 

'only' 20. lmao.

 

dude, you should feel lucky to get 20mpg.. Im not sure what im getting in my truck right now as i just got it back, but i know its no where near 20.. my jeep.. HA.. try 170 miles per TANK... you do the math

 

I mean, I understand that bigger tires = less mpg but I was just wanting to know if it is going to increase any with the gear change. I was getting 24 highway now 19.

 

from what i understand about gears and larger tires, once you get bigger tires, if you stay with the high gears, ie, 3.73's, your truck is going to have to work harder.. less mpg.. Lower gears, ie 4.10, 4.56, less work, higher mpg..

i could be wrong though..

 

you will probably see some of an increase but probably not back to 24 mpg

 

Ya you would see an increase but lose top speed i think?

 

Are you sure you're calculating it correctly? With 31" tires (stock is about 27.5") your speedometer,
odometer are going to read about 13% slow. That is when the odometer says you have traveled 100 miles.
You have actually traveled 113. Using that as a basis, if your odometer says you have traveled 100 miles
and you use 5 gals, that would indicate your getting 20 MPG.
However if you have actually traveled 113 and use 5 gals, your mileage would be about 23. Pretty close.
Easiest way to find out, is to check your odometer against the mile markers on the hwys. Pref an interstate.

 

Top speed would be about the same. Lower gearing would be offset by the
larger diameter of the tires. If the tire size remained stock, then you would lose
top speed because you would reach max RPM at a slower speed.

 

I am using a scan gauge to see what I am getting. And I did already change the scan gauge to 13% when I got it at xmas.

So, looks like spring break I need to go to the junkyard and find me a rear end. Hopefully this time I will find one unlike the last 20.

 

I've spent a lot of time in the last 6 months studying MPG at 70mph. (I have a FX4 w/4.10s)

What you need to look at more than anything is "load". Reducing load will gain you the most mpg.

Things like headwind, height off the ground, dragging brakes, being behind another car/truck, ambient temps, rpms, & timing (vs the octane used) all play a part in "load".

As load goes up.. timing goes down & fuel gets added.

Just going from 3.73s to 4.10s alone will do two things at 70mph. Load will go down.. and rpms will go up. So your gaining in one area and loosing in another.


IMO.. adjusting the timing VIA a tune would give you more feeling of power than the gear swap would.

 

I have 4.10 gears and im only getting 15 mpg city and 19 highway, i think you would get better gas millage if you stayed with the 3.73 gears

 

I think you'll pick up some mileage swapping to 4.10 gears. It won't be as good as stock, but it will help.
Hell a lot of the 4 cyl rangers come with 4.10's from the factory with 225's or whatever, you could probably afford to swap to 4.30's with 31's.
My Jetta (6 speed vr6) runs high rpm's on the highway (around 3000rpm at 70mph), but gets 28-30mpg at that speed. Sure, the rpm's are high, but it requires little throttle (little load).

 

I still have not found what I want at the junkyard. Hopefully something will come up soon.

 

I have a 05 ranger with the 4:10 gears. They came with the truck from day one. I get terrible mileage usually... sometime if I drive really really nice I get 17 combined. The truck does feel like it has more power with them. But if I was not going to get teh truck brand new for 16k (whicha t the time it was a really good deal).... I would have ordered the truck with teh 3.73, I believe the fuel economy would have been better.

Also I noticed with the 4:10 my truck wants to roast the tires if its any bit wet out... but im not gear head... just seems like it to me compared to the old f150 1992 I had with the 373 and a standard... I have an auto now.

 

You have a 4.0, he has the 2.5 huge difference. I think the 4.10 would help, would compensate for the taller tires and bring you back closer to stock.

 

Apples to oranges comparison. Different engine, transmission.

Even the new 4.0L engines can be slugs with 4x4 and 3.73 gears, especially if you're towing or hauling (it is a truck after all).
The SOHC 4.0L doesn't have as much low end as the older OHV 4.0L, but it revs much higher and smoother, and makes more top end power, which is why the 4.10's work well with it.
I got 18 mpg on the highway a few times with the sport trac in stock condition with 4.10's and 255/70/16's.

 

I got 18 mpg at 80 mph and my yzf 450 in the bed. Your truck is struggling with your tire size so you need to upgrade to 4.10 and your mpg will come back. Not fully but close.

 

Ya, I know it wont be fully but the mileage will hopefully be a little better and get me back to stock power band.

I just need to find what I am looking for in the junkyard still. I go every chance I get.

 

yea this is why i wasnt even willing to up to 29" tires ... actually went down a size im ridin 215/70/15's lol

 

good luck!