I'm about to pull the trigger on a 2012 S.D. 6.7L 4x4 XLT Supercab Longbox seems all I can find is rigs with 3.31 gearing....I really want the 3.55 gears. Dealer is telling me the combination of the 6.7L with the new Auto Transmission is more than adequate for hauling. I will be hauling an Eagle Camp 950 Truck Camper along with a 10 foot toy hauler trailer....I'm not a freeway runner mainly secondary roads and mountainous terrain. I'm used to 3.73 gears and before than 4.10 gears.

Sure would like to hear user opinions and experiences.

GARY

 

I have a 2012 Suoercab 4x4 with 3.55s with 20 inch wheels but its just my car. The 3.31s have smaller wheels making the difference not much.
I think the longer body needs the larger wheels to look right.

 

I have a 2011 Ford F250 6.7L deisel with the 3.31 gears, and have no problem hauling my 5th wheel. The 5th wheel weight is 13700lbs tows her no problem sometimes I have to look back and make sure it is still there and I live in Nova Scotia Canada.

 

Broaden the dealers that you are searching their inventory. Plenty of 3.55 around.

But as mentioned, If you stay with the 3.31 and 18" tires. You will be fine. The difference in tire size pretty much negates the gearing difference.

 

Ford shows no difference in towing capacities between the 2 ratios...I guess when you have 800# torque under your right foot it doesn't matter.

 

I also have the 3.31's. The thing pulls like it's stupid. I tow a 25' Airstream and I don't even feel it. Great mileage and crazy power.

I worried about the gearing prior to purchase but this thing has crazy torque. Don't worry about it.

 

My truck has not pulled more than 8,000 but up and down hills I still don't know the trailer is back there.
3.31 with 18 inch wheels (with 295 70 Nitto Terra Graplers) and I don't worry about it.
I had pre-ordered mine in March 2010 with the 3.31.
As the 12 weeks went by as I waited, I started to second guess the 3.31 decision but it turns out, I worried for no reason.

 

I have an 2011 F350 with 3.31 pulling a 5th wheel up I17 in Arizona with no issues at all, lots of power pulling that grade.

 

No issues at all with mine either. The 3:31 on my long bed works great.

 

In 2011, the 3.31 came with 18" wheels and the 3.55 came with 20" wheels. They have equivalent torque.

I'm pulling a 14,000 lb 5er with a 2011 F-250 with 18" wheels and the 3.31 and it's absolutely fantastic. I literally have to remind myself that it's back there when I'm driving.

 

Thats not entirely true I have a 2011 F250 with the 18" wheels and 3.55. So don't assume that because it has the 18" wheels it has the 3.31.

 

I'm pulling 7K with mine... no problem and stays in 6th gear until I drop below 50 mph.. boost goes up a little on hills but no hunting gears..

 

26800 lbs with a srw 350 with 3.31. Green Bay, WI to western burbs of Chicago. Put it in "M" and she pulled like a champ(95+ degrees outside air temp).

 

I just got rid a '12 w/3.31's and did not like how much it hunted for gears. I personally get the 3.55's w/18" wheels. The problem was, by the time i got to the bottom of a hill it was wanting to drop into 5th, and by the time i was part way up the hill it was wanting to drop into 4th and rev to about 3k rpms!! If i had wanted to rev that high i would have bought a gasser.

I wanted 3.55's to begin with, but let the dealership talk me into 3.31's, and really regretted it. I also wanted to put 285 tires on, but didn't dare since i was already struggling to pull the hills. DEFINATLEY GET THE 3.55'S W/18"S

 

I have 2011 long box crew that I ordered with 18 inch tires and 331 gearing,it pulls absolutely great. I have 39000 miles most of which are pulling a 11000 pound 5th wheel or a horse trailer weighing 8000 pounds including the horses. I pull the horse trailer to the mountains all the time. I have pulled the 5th wheel all over the western half of the United States with no trouble at all. With 800 pounds of torque you have more power than you will need. If shifting down bothers you lock the transmission out of the highest gear on hills. I would order 331 gears all over again.