Towing with 3.31 rear end
Lead Driver
Joined: Jun 2005
Posts: 8,457
Likes: 722
From: Calgary Canada
I don't have a 2015, but I do have the 3.31, so hopefully my experience is helpful.
I went from a 2005 5.4L with 3.73 gears to a 2012 3.5EB with 3.31 gears, and pulling the same trailer on the same ground, the 2012 was far more powerful. I upgraded to a bigger trailer (now 7000 lbs), and I don't find myself lacking for power up hills or when passing.
What I have considered, is that with the 3.31 gears, I'm probably dropping down about one gear further than someone with the 3.73 would need to, but that doesn't bother me.
I climb a lot of hills while towing in 4th gear, and if there is any kind of headwind, I'm in 5th most of the time on the flats.
Now, that's a pretty apples-to-oranges comparison, I realize, but I have been wondering what gears I would buy on my next truck, and I have decided that I would have no problem getting the 3.31's again.
Also, I suspect my empty highway mileage is slightly better with the 3.31's than it would be with the 3.73 or 3.55. Maybe not much, I'm not sure.
I went from a 2005 5.4L with 3.73 gears to a 2012 3.5EB with 3.31 gears, and pulling the same trailer on the same ground, the 2012 was far more powerful. I upgraded to a bigger trailer (now 7000 lbs), and I don't find myself lacking for power up hills or when passing.
What I have considered, is that with the 3.31 gears, I'm probably dropping down about one gear further than someone with the 3.73 would need to, but that doesn't bother me.
I climb a lot of hills while towing in 4th gear, and if there is any kind of headwind, I'm in 5th most of the time on the flats.
Now, that's a pretty apples-to-oranges comparison, I realize, but I have been wondering what gears I would buy on my next truck, and I have decided that I would have no problem getting the 3.31's again.
Also, I suspect my empty highway mileage is slightly better with the 3.31's than it would be with the 3.73 or 3.55. Maybe not much, I'm not sure.
Postmaster
Joined: Jun 2014
Posts: 2,775
Likes: 7
From: Lewisberry, Penn
If you are buying the truck because you tow often then you should seek out 3.73 (or at least 3.55). If you tow a few times a year and the rest of the time you just drive around then the 3.31 will give you good savings in fuel, and long term you are spinning the motor less so you put that much less wear on the motor as well.
Super Moderator
Joined: Jan 2008
Posts: 39,979
Likes: 1,512
From: Maine, Virginia
I haven't had any issues what so ever but it's important to remember the limitations of your truck. My 2011 with the 3.31's is rated to tow about 9000 lbs.
I can remember not too long ago when the 3.73 LS axle was the go to or must have to make a truck a truck. IMHO, that set up will become a special order or even an obsolete item in the future.
I can remember not too long ago when the 3.73 LS axle was the go to or must have to make a truck a truck. IMHO, that set up will become a special order or even an obsolete item in the future.
Lead Driver
Joined: Jun 2005
Posts: 8,457
Likes: 722
From: Calgary Canada
With the upcoming 10 speed transmission, I don't see the need for a non-commercial truck owner to have the 3.73 gears.
Only kind of off-topic, but does anyone know the planned gear ratios for that 10-speed? I am guessing it'll be a triple overdrive, and have a very deep first gear.
Only kind of off-topic, but does anyone know the planned gear ratios for that 10-speed? I am guessing it'll be a triple overdrive, and have a very deep first gear.
Lead Driver
Joined: May 2015
Posts: 5,868
Likes: 356
From: Mts. S. of San Francisco
With the upcoming 10 speed transmission, I don't see the need for a non-commercial truck owner to have the 3.73 gears.
Only kind of off-topic, but does anyone know the planned gear ratios for that 10-speed? I am guessing it'll be a triple overdrive, and have a very deep first gear.
Only kind of off-topic, but does anyone know the planned gear ratios for that 10-speed? I am guessing it'll be a triple overdrive, and have a very deep first gear.
EDIT: Didn't find a thread, but I did find this discussion: Exclusive: An Inside Look At Ford's New 10 Speed Transmission - The Truth About Cars.
It speculates that there will be 6 underdrive gears, one 1:1 gear, and 3 overdrive gears, along with guesses of the approximate ratios.
Fleet Mechanic
Joined: Jun 2006
Posts: 1,684
Likes: 2
3.73 was not available in my combination, but I made sure mine had 3.55's. Dealer had to trade.
Trending Topics
Junior User
Joined: Dec 2006
Posts: 99
Likes: 0
From: Acworth, Ga
I have a 3.5 eb with 3.55's. The dealer gave me a loaner with a 2.7 and 3.31's... I was very surprised at how well it towed!
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!
Michael S. Palmer
10 Most Surprising 2026 Ford Truck Features!
Joe Kucinski
Top 10 Ford Trucks Coming to Mecum Indy 2026
Brett Foote
5 Best / 5 Worst Ford Truck Wheels of All Time
Joe Kucinski
Ford Super Duty: 5 Things Owners LOVE, 5 Things They LOATHE!
Joe Kucinski
Every 2026 Ford Truck Engine RANKED from WORST to FIRST!
Michael S. Palmer
The Best F-150 Deal of Every Trim Level (XL through Raptor)
Joe Kucinski
Fleet Mechanic
Joined: Jan 2011
Posts: 1,493
Likes: 21
I want to get 3.31s next time. I don't have mountains to deal with and based on my past experiences with trucks, the taller your gears are the better fuel economy will be. (I have 3.73s in my 2013, but if I get another truck, Im keeping the 2013, as its a rare truck..)
Elder User
Joined: Dec 2008
Posts: 705
Likes: 1
From: Clay Country, GA, NE MS
Right boys, I'm a geezer, so I'm really having to relearn all my old fashioned differential ratio stuff from the '60s era. Actually, there is a whole heap of mess I'm having to relearn... daggoned world keeps changing on on me. Right in front of me old bifocaled eyes.
Mountain Pass
Joined: Aug 2004
Posts: 147
Likes: 2
From: Iowa
I have 3.31's in my 2013 3.5L EB. For just driving around and long trips, I love it. The last longer trip I took was 235 miles each way. Going out got 24 mpg and coming home I got 22 mpg. Have to love that 
I used the same truck when I moved to Alaska, and pulled a 14' x 7' enclosed trailer, and averaged 9 mpg over the 3200 miles. If I was pulling a trailer weekly, I would have probably preferred the 3.55's but for my occasional use, the 3.31's work just fine, especially being able manually shift if needed.
I used the same truck when I moved to Alaska, and pulled a 14' x 7' enclosed trailer, and averaged 9 mpg over the 3200 miles. If I was pulling a trailer weekly, I would have probably preferred the 3.55's but for my occasional use, the 3.31's work just fine, especially being able manually shift if needed.
