# Ecoboost 355 or 373 rear end?



## DA REEL DADDY (Jun 7, 2005)

I have been looking in getting a new Ford Echboost too. I tow a 19' bay boat regularly, but not far, (maybe a trip a year from Houston to Mansfield) and a 16' trailer with two four during deer season. Like everyone else on here too probably.

If I buy another travel trailer in the future it will be under 25', but that is a BIG maybe.

With little towing I do y'all still think it would be beneficial to purchase with the higher 3.73? 

What maybe the MPG between the 3.55 and 3.73


----------



## C.Hern5972 (Jul 17, 2009)

i have the 3:55 in mine. numbers posted in other posts. ill have to search


----------



## JFolm (Apr 22, 2012)

What will 80% of your driving be? City/highway?


----------



## DA REEL DADDY (Jun 7, 2005)

80% will definitely be city more small town, if that is city and driving from Fort Bend to coast.


----------



## ReelWork (May 21, 2004)

Go 3.73 if you have the choice. My previous f150 had 3.55s and while it was decent towing, after I bumped the tire size up a size and towed some heavier loads I found the truck to be a little anemic (due to the gearing). So do yourself a favor, you already have possible plans for a larger RV and who knows what else...lean forward a little and get the 3.73's - you won't regret it.


----------



## TheGoose (Jan 22, 2006)

I have 3.55's and I'm not pleased with my gas mileage (15-16 combined). I think that for pure highway driving the 3.55's are better but maybe the 3.73's are better for combined. I know that sounds opposite of the truth but I think that maybe the 3.73's allow the engine to get up to it's "sweet spot" easier. 

I've often wanted to see what it would cost to swap to 3.73's but never have checked into it.


----------



## Gottagofishin (Dec 17, 2005)

I have the 3.73 and do a fair amount of towing. The 19 ft bay boat will be no problem at all. 

I tow 6000-7000 lbs regularly, and I just lock out 6th gear on the heavy loads. It's basically the final drive equivalent of a lower speed rear end. With 6th locked out it runs at about 2200 rpm at 75 (which is nothing for a gas engine). The tranny runs cooler because it isn't downshifting on hills and it actually gets better gas mileage since the engine isn't lugging. 

If you towed heavier loads most of the time, I would say the lower speed rear. But you don't so get the 3.73 and just lock out 6th when you get your TT.


----------



## fireguy (Jun 28, 2010)

On other forums I have read the 3.73 behind the ecoboost gets terrible fuel mileage, here you guys state not so, i've also read the 3.55 is the way you want to go for pulling and for fuel mileage. Confused on this issue, but i don't own one you guys do, and i'm considering getting one, things that make you go hmmm.....


----------



## paragod (Aug 25, 2006)

I shopped that truck real hard when I was buying last yr I chickened out and got another diesel but was going toward the 3.73 rear end. Since I do tow a lot and from what I was told that rear end comes in the max tow package and it was hard to find. It will get low MPG I did get the 3.73 in my current truck and get about 3-4 mpg less than co worker with a 3.45 rear end same truck.


----------



## louie870 (Apr 20, 2011)

I just bought one, 4x4, ecoboost with the 3.55 rear end. I only have 530 miles on the truck but back and forth to houston a couple of times and city driving Im averaging around 16.5-17.7 mpg. If I reset the lie-o-metter while doing 75mph down the highway, it stays right at 19.5mpg. I have not pulled anything with it yet.


----------



## Brute (Apr 29, 2009)

3.73 Especially if you plan on putting any thing other than stock tires on it. 

Not sure if it is still true but they use to say you lose .1 on your gear ratio for every 1" of tire height you gain. A lot of people are wearing out transmissions by running real high gear with larger tires. Just a 285 can increase you 2-3" over stock.


----------



## DA REEL DADDY (Jun 7, 2005)

Hey folks thanks for the responses. I had not got rid of my power stroke yet and have been driving to the lease often. I tell ya that old truck is sure treating me right and that it is why I had not made a move on a new one.


----------

