What gears should i be running for Optimum Fuel Mileage in 2001 Ford F250 Power Stroke with 6 inch lift, 36"x15.50 Mickey Baja ATZ, cold air intake and larger exhaust. I currently have the stock 3.73 gears.

 

Where do you drive, flat or mountains, towing or commuting? You want optimum mileage overall (like at the end of the year), or do you want optimum mileage towing, or optimum mileage during the week driving to work? Or, at the end of your life do you want to be able to say you got the optimum mileage?

 

3.73 is a good gear if you want fuel mileage. Get rid if the lift and put some stock size tires on it if you want more fuel mileage. A 6 inch lift really kills your MPG.

 

Very first off, welcome to FTE We're gonna get you learned up in a hurry.

You're basically asking how to save pennies while driving a brick house on wheels. Even 2-4mpgs lost because of your lift and tires isn't that much money in the long run, and the time it'll take you to recoup the cost of a front and rear regear to get a 1-2mpg improvement is probably longer than the life of the truck. Regearing just changes where your speed in a certain gear falls on the powerband, making more torque available at slower speeds.

That being said, 4.30s will take you to (almost)stock, 4.56s will give you more power, and 4.10s won't be a big enough change to matter. I don't even know if 4.88s are available for the D50 axle, but if they are it'll probably involve a carrier replacement.


EDIT: Your sig/profile don't list an engine. I always assume people have diesel trucks and that's what I tend to unintentionally bias my opinions towards. If you have a gas engine, going to 4.30s will be the best decision you ever made, not for MPGs, but just general driveability. If you DO have a gas engine, there's a few threads I can point you to that beat this topic to death that'll help you make up your mind.

 

Thanks for the replys. I know its a tank on wheels but there is no way I would go back to stock, it looks just to damn good. I was just curious, it's not a major issue. And sorry about not listing the engine in profile yet, but I have the 7.3 Power Stroke, looked everwhere for it and found one with under 100,000 miles.

 

If you do a search online for gear ratio calculator or some such you'll likely find a "spreadsheet" that shows a range for tire sizes. I think Fourwheeler used to have one. Anyway, it would show for any given tire size a scale from mpg, in between, and power. So, you'd have a high gearing, say 3.73 for mileage, 4.30 for average driving, and 4.88 for power. Try searching for something like gear ratio chart.

 

Again thanks for the help guys. I'll probably just keep the 3.73 that are in it. It does have a small whine coming from the rear when accelerating. Maybe it gets to bad I might change to a higher ratio, but probably keep the same.

 

Per Bryan and an expensive learning experience for myself, if you're looking to recover some fuel economy and lighten the load to stock specs, 4.30 gears are best. 4.30s will keep your truck in the stock power band (with your 37s) and make it easier to get and keep you truck moving. 4.10 gears are only if you're running 35s like me...

 

With the 7.3L's lower power band I wouldn't go lower than 4.10s if you want to run 70 mph our more. That's such a small change I'd probably leave it alone. 4.30s would be good for town/hilly driving and transmission life, but will hurt your 70+ mph highway mileage some. I run 4.30s with 35s on my 6.0L and keep it under 70mph.