4.56 gears?

[Dirtman]

My around town mileage sucks. And my general theory is because the stupid thing shifts into overdrive at like 35-40mph and then the engine is working its ass off to keep up. Going to a lower gear should help take strain off the engine in stop and go low speed driving like I do. My truck rarely sees the highway so I have no fear of big gears.

I even considered 4.88s but I do plan on a few trips to Georgia with it so I dont want to flat out murder my highway cruising ability.

 

[sgtsandman]

Around town, I dropped from about 16 mpg average to about 15. I could get better than 15 but like to accelerate too much. I could get over 20 mpg with the 4.10 gears if I a kept it under 65 mph but in the range of 18 to 19 mpg at just over 70 mph. I get 17 to 18 mpg doing just over 70 mph with the 4.56 gears. So basically dropped about 1 mpg both city and highway driving. As I said before, my towing gas mileage actually improved about 1 mpg with the 4.56 gears with 31" tires.

Based on that, my expectation was a bit low then. Most of the highways that I travel around here are interstates with 65-70 mph speed limits. Thanks for the info.

 

[Bgunner]

Since @RonD brought this up and it pertains to gear ratios and tire size, is there a chart or equation the calculates tires size and gear and ratio to stock ratio? I'm not a math wiz so charts help keep me balanced but I do know how to use equations once I know the formula.

 

[sgtsandman]

Since @RonD brought this up and it pertains to gear ratios and tire size, is there a chart or equation the calculates tires size and gear and ratio to stock ratio? I'm not a math wiz so charts help keep me balanced but I do know how to use equations once I know the formula.

There is. I believe it’s in the tech section where the tire/gear ratio chart is. There might even be links right in the chart is. I think it’s in the axle section.

 

[Bgunner]

https://www.therangerstation.com/how-to_pages/gear_ratio_tire_size_chart.shtml

Here is the chart but what engine is it based upon?
There are 4 and 6 cylinders stock and each having a different version and output to it.
While this is a "general over all" ratio it all depends on output of the motor, HP + Torque, to what either best fuel economy, best performance, and best towing should be. Obviously a 4.0 will easily out tow a 2.3 non turbo motor at the same gear ratio so this is where my concern is with this chart.

Is there an equation for HP, Torque, gear ratio and tire size out there? Or am I just hoping for the unicorn to show itself with this question?

 

[sgtsandman]

It’s a general chart based on the drivetrain, not the engine. To be more specific, you would need to get the gear ratios for your specific transmission and the differential and throw them into a formula for specific speed ranges for each gear. This is only based on one particular speed and gear ratio most transmissions have at that speed to figure what the engine rpm would be. Factors like horsepower and torque are not considered.

 

[pjtoledo]

https://www.therangerstation.com/how-to_pages/gear_ratio_tire_size_chart.shtml

Here is the chart but what engine is it based upon?
There are 4 and 6 cylinders stock and each having a different version and output to it.
While this is a "general over all" ratio it all depends on output of the motor, HP + Torque, to what either best fuel economy, best performance, and best towing should be. Obviously a 4.0 will easily out tow a 2.3 non turbo motor at the same gear ratio so this is where my concern is with this chart.

Is there an equation for HP, Torque, gear ratio and tire size out there? Or am I just hoping for the unicorn to show itself with this question?

what you are asking can be a complicated answer.
the simplified version is a 2 step process.
first choose an engine and find it's brake specific fuel consumption. (google it)
that will give you the power output at any given rpm, and how much fuel it needs to do it.
which means: it shows what rpms where the engine is most efficient, and/or where it makes the most power.
then use gear ratios to match what you want to do with what the engine does.


the " 'ol timers" method is to use an intake vacuum gauge.
higher vacuum readings mean less air is being sucked in, which means less fuel is being used.
sort of a low tech efficiency monitor.