I'm trying to figure out if I should re gear my truck. I have a 2010 F150 Lariat 4x4. Stock tires were 275/55/20 and I recently put 33" cooper STT tires on. My gas mileage dropped to 13 around town, maybe 13.5 or a little better on the highway. RPM's are about ~1800 at 70mph.

I am having a hard time finding information about re gearing. I would love to get a little bit of my power back, but would also love to get better gas mileage. I'm not sure if that is possible at all. I'm thinking my stock gears are 3.73, would it be better to go up (say to 4.10) or to go down?

Can someone explain the what would happen if I went down, or if I went up? I know you can re gear to get better power, but can I re gear and get better fuel economy? Would it be worth it? Thanks for any advice you can give me!!!

 

Long story short, no it is not worth it. You will be looking at around $1,000/differential. Since you have a 4x4 you will have to replace the gears in the front and rear diff. You have poor gas mileage now because of your bigger tires, the minimal savings in mileage that you "might" get from re-gearing are not worth the expense it cost to re-gear, besides re-gearing is typically to recoup power not gas mileage. A tune might be in your future tho, it will get you some power back, re-calibrate your speedometer and you might get a mile or two per gallon back.

 

Yea, that's what I was kinda thinking. Well maybe I'll consider a chip/programmer. Thanks for the advice

 

you only went up about 1" with the Coopers. the weight and tread pattern on that tire is what is causing the lost mpg. not much you can do, i doubt a programmer will do very much.

 

Just as an aside, lower gears are a numerically higher number. So if I went from 3.55 to 4.56 I'd be getting lower, or shorter, gearing.

 

Yea I'm not sure I want to drop $500+ on a programmer to not get results to make it worth it anyway. Gonna put a cold air intake and exhaust on in the future, so maybe I'll see some sort of increase on my mpg's

 

Ok thanks, this is really the info I wanted to know. Which it makes sense, shorter gears= a little more power to the wheels

 

Your 32"s went to 33"s, ~3% bigger.
Going from your stock 3.73s to 4.10s is ~10% lower.

 

I would have to agree not to regear I dont think the $1000 you spend will save you that much in gas

 

If you are only getting 13 MPG you need to change your driving style.