I will be getting another 5.0L when I buy new again and I was wondering if there is a noticeable mpg difference between the 3.55 or the 3.73 rear end?

 

Take this with a grain of salt: It has been said that the gear ratio has little effect on mileage in average, combined driving. A steeper ratio will allow the vehicle to accelerate easier, for better economy in stop-and-go, and doesn't give up much on the highway.
Add weight, and the mileage gets closer.
The real key, I have been told, is RPM at your typical speed, and the torque peak of the engine. The torque peak is the most efficient operating point, so if the ratio places you right there at your preferred speed you should find that to be the bet mileage you will get on the highway.

 

Thanks for the detailed information... Makes sense.

 

I had two almost identical Z71's. One was a 1994 with 3.73's and 245/70/16 road tires. The other (I still have this one) has 3.42's and 265/75/17 road tires. In mostly highway driving, the lower geared, slightly smaller tired truck got about 1 mpg better...which is the exact opposite of what I would've thought. Now since both trucks have over 200k miles, various stages of engine tune probably come into play. But the truck with lower gears got slightly better mpg and was more fun to drive. I plan on getting 3.73's if/when I get a new F150. If I go eco, I will probably get 3.55's. If you get right down to it, the mpg difference between 3.73's and 3.55's in the 5.0 will probably be so slight, it won't matter. If you drive one with 3.73's and like the added power, the .5 mpg difference one way or the other won't really be noticeable in you bank account.

 

I want/like a peppy truck but don't want the mpg to suffer too Mich.

I realize the 3.73s will give it that plus I will most likely level and put larger tires too.

Thanks for your comments.

 

I don't think the 3.73's vs 3.55's will hurt you much. if you do go with larger tires, the 3.73's may even yield better mpg than the 3.55's, especially if you're not driving all highway.

 

I had 3.31's in my 2wd 5.0. My 4wd 5.0 has 3.55's. Don't notice too much different in power or fuel economy.

Lighter 2wd Truck + 3.31's = similar mpg's to heavier 4wd truck + 3.55's.

When all is said and done I'd get the 3.73's, I'd rather be looking at them then looking for them. Just my 0.02.

 

I was thinking the same. All your comments just helped me solidify my decision.

It will be a 4x4 with the 5.0L and 3.73s.

Keep em coming.