huntbig

I've been trying to navigate the infinite number of posts and topics hear and can't really find the answer I'm looking for. I'm looking to down size to an ecoboost from a 6.0 powerstroke. I no longer need a power stroke would like a truck with better milage( better then the 13/15 mpg average I'm getting). The truck would be my daily driver used also for hunting, hauling wood, pulling a 12' landscape trailer with a fourwheeler and wood on it(maybe 1 month out of the year MAX), pulling a 20' site trailer 10 miles twice a year, basically just using it as a truck.
My big question is which gearing should I look at for best over all performance and milage in a Scab, lariat, 6.5' bed, 4x4

TJPlatinumEB

3.55 has shown to be a pretty mix for mileage while not losing much in the power and towing needs too. You will find that a lot of people who are complaining about mileage are 4x4 w/ 3.73's. Not ALL of them, but a good bunch of them.

I daily drive mine and have towed my Supra in an enclosed car trailer weighing about 6500lbs loaded down 4 times now without issue. Each time was over 200 miles and each time was through the very hilly and up and down terrain here in the TX hill country.

I also test drove a truck w/ the 3.73's and was given it as a loaner for a week while I waited for my truck to arrive and honestly couldn't tell much difference at all in the performance of it or how either one drove any different. My 3.55's though can get 22-23mpg at 72-74mph no problem. The 3.73 truck I had was a good 2-3mpg lower on the exact same trip.

AC Man

I don't think you can get 355 gears in a FX 4. Mine has 373. It depends on wether you are going to put large tires on it. I have Raptor wheels and 315 x 70 x 17 tires (34.5" tall) If I had a choice, I would have gone with the 410 gears, which basically puts it back to 373. I do have a little bogging with the larger tires. Hoping a programer and adjusting the tire size will help.

EricTheOracle

When I saw the title of your thread I had thought 3.31 but since I see that you'll drive with a trailer, 3.55. If you want to simulate a shorter gear, lock out 6th gear.

A 3.55 ecoboost will pull sixth gear from 45 mph on.

If you know that you'll never pull anything too heavy, 3.31.

The 3.31 will allow a faster cruise without getting into the turbos and parabolic fuel use.

I'll put it to you this way: I have 3.55 and wish I had taller gears and I use my truck as a truck (with limited towing). With mandated ethanol blending, I get 13-14 mpg in the winter and 17-18 mpg in the summer. If I drive like Mrs. Daisy at 55 mph, I can see 23.5 mph on a cruise. But then the road slows, or I need to gas it and I'm back to 17-18 mpg in the summer.

Slate 150

3.31 or 3.55 anything you get will get the job done with out a sweat. 3.55 if you plan on bigger tires in the future. If I had to do it over I would have went 3.31 for the low rpm cruize. A 3.55 at 65 mph is 1600 rpm in 6th
2200 rpm in 5th
2700 rpm in 4th
Really not a big deal because as you need more power the motor starts boosting first rather than downshifting first. Main thing though if your off road is get the locking rear so you can turn off all the so called traction devices

huntbig

I think I'm debating between the 3.31 and the 3.55.

I plan on keeping the truck entirely stock, aside from throwing a cap on the back. I was toying with the idea of possibly having it come with with 20" wheels; would this effect the choice of gear I should go with?

EricTheOracle

If you're really into it, get an open diff and put the $250 (or is it $300 now?) toward an Eaton TrueTrac rear differential which is hands down, the best limited slip in the business.

FWIW, here in Minnesota, I found the 20" wheels far too harsh on our frost-heaved roads and so I went with 18" wheels which ride better.

By better I mean the ride is more compliant and the bumps are dampened more by the extra sidewall in the tires.

huntbig

Is there any noticeable difference in towing ability and highway mpg's with the 3.31 compared to 3.55?

Slate 150

From the factory very little. Outside the tire is roughly the same. Like eric said less sidewall should handle better laterally less roll at the expense of comfort ride. There seems to be a lot more aftermarket tires available in the 20 size though.

EricTheOracle

You just told us that what you occasionally tow only one month out of the year and that it isn't much weight (an ATV and some wood and some woods likely means less than 5,000 pounds of wood—unless you're making the redneck tree-stand from hell). Which means that at the end of the day, your concern is mostly how tall of a gear can you get away with to preserve the best mpg given the expected use your shared with us.

3.31.