CPT150

aggree with ultradriver minus the burn out thing if your not into that, "better to have and not need than need and not have." If MPG is minimal gain/loss and larger gear ratio equates to higher torque, whats the issue. 3.73 IMO. good luck

TwinTurboFx4

Spend the extra money for 3.73s. It will help with resale and the mileage loss is like half a mpg.

byoungblood

You won't notice the difference between those and 3.55s.

You would have to go with 3.31s or less to get a repeatable difference in mileage.

Adobe2X

Get the 3.73's. The difference in MPG will be negligible and you will love how well the EB stays in 6th gear on the highway.
When you are traveling at 75, you will be RIGHT at the lower end of the torque peak (2,000 to 2,100 rpm) which is the sweet spot for the EB and where it makes a lot of power.

mechanicboy

3.55 for four reasons.

1. More economical (mpg). It might be a small difference but a little bit will go a long ways if you keep the truck a long time.

2. Cheaper upfront costs, no paying for something that doesn't cost anymore to make.

3. It will tow 7,000 no sweat. My 5.0 towed a flat face 30' trailer of the same weight no problem with less torque.

4. It's the fastest(unloaded) gearset. Check the 1/4 times and reference them to the gears.

Hunttman01

Whatever you get, get the limited slip, or locking differential. One time offroading or driving up a slick boat launch and you'll thank me

zx12-iowa

I have had 3 f150s. 2 with355 an 1 with 373. The 3.73 was a much bigger diff on earlier generations. With the Eco, the 3.55 moves my 6k pound double axle trailered 23' boat with ease and rarely shifts out of 6th. Big diff from my 5.4 with 3.55.

Would the 3.73 tow better. Yes by a smidge. But you don't need it at all and empty with cruise on your mpg will be better than .5 mpg. Based on my previous trucks the diff is worth on average 1-2 mpg. Agin the diff is more the steadier you cruise. Stop and go and always on the gas and they are closer to same mpg in my real world experience.

So it depends on what you want bc you absolutely don't need it. In fact if I stomp the gas with my boat attached, if damp my rears will spin with the 3.55, and stuff in bed. Yes crap stock tires but point is there is plenty of torque to pull your boat with ease.

SIC_HDPP

If you wanted the max towing package you would need to get the 3.73 or the 4.10's. The package includes the towing mirrors, an upgraded oil cooler, and the receiver is reinforced (from what I have seen here on the fourm). You aren't towing long distances often so that's a tough choice.

engineermike

This goes back to my point earlier. Up until 2009, the F150 had the 4R75 transmission, which had lazy 2.84, 1.55, and 1.0 ratios for the first 3 gears. You had to use a short rear gear to get a decent mechanical advantage for towing. The new 6R80 has much more advantageous 4.17, 2.34, 1.52, and 1.14 ratios. The rear gear becomes much less a factor with these in the transmission, hence the 9000 lb tow rating with even the tallest rear gears.

Syclone Rob

If you are going with the ecoboost, I would get the 3.55 as its a good balance between the 3 gears offereed. Also I find turbo engines do seem to work a bit better with a lower (numerical) rear.