Looking into the possibility of a new to me TV. I just looked at a 2012 F250 with a 6.7 and 3:31 gears. What I would like to know is if anyone here tows with this set-up and how it works. I realize that 3:31s are not normally the ideal choice for towing but since this is a diesel, it may be different. I realize that 4:10s or 3:73s would be a better choice. Buying used you do not always have a choice of the perfect unit.The truck appears to have towed since it does have what I guess are part of the mount for a fifth wheel hitch in the bed. Also it appears to have the tow package just not the best set of gears.Not trying to start a feud as to what is best, just trying to get comments and advice on this set-up. Thanks in advance for all of the help.

Actually there is little choice and the gearing will be fine. 3.31 was used with 18" wheels and 3.55 was used with 20" wheels. The overall effect was the same with the engine turning the same RPM at the same speed. One exception is that the snow plow preparation package and the camper package had the 3.55 with 18" wheels. A diesel turns at a much lower RPM than a gas engine and you should not compare the gearing between the two. Now if you really want something to unnecessarily worry about, consider the fact that 5th gear is overdrive and 6th gear is over overdrive.

3.31 is fine for towing and gets better fuel economy than 3.55. The 3.31 is mated with smaller tires than the 3.55 but the difference between the 275/70r18's and 275/65r20's is only 2.7%. If the 20 inch tire option was mated with a 3.40 gear ratio the engine rpm would be identical to 18" tires and 3.31 gears. So when the engine of the 3.31 equipped truck is turning 1400 rpm the engine of the 3.55 equipped truck with 20" wheels will be turning 1461 rpm if both trucks are traveling the same speed.

Thats one of the reasons they put so many gears behind the newer motors. Choices. When you get to a climb, simply manually drop a gear or two to maintain the RPM in the power band.

I towed for 4 seasons with a 2013 F250 6.7 with the 3.31's, it worked fantastic and was decent on fuel. the only time I even wished for more gears was taking off from a dead stop trying to merge and even then it was quite good.

Pulled a 36 foot 5th wheel with a 2016 PS diesel and 3:55 gears. Pulled same load with 2017 PS diesel and 3:31 gears. Both 18 inch wheels and same size tires. 2017 had more power and torque on paper but I couldn’t tell the difference. Also didn’t notice any difference in rpm at cruising speed according to the tachometer.

3:31 Gearing | Good Sam Community

Lynnmor
Explorer
Apr 09, 2018
Actually there is little choice and the gearing will be fine. 3.31 was used with 18" wheels and 3.55 was used with 20" wheels. The overall effect was the same with the engine turning the same RPM at the same speed. One exception is that the snow plow preparation package and the camper package had the 3.55 with 18" wheels. A diesel turns at a much lower RPM than a gas engine and you should not compare the gearing between the two. Now if you really want something to unnecessarily worry about, consider the fact that 5th gear is overdrive and 6th gear is over overdrive.
4x4ord
Explorer III
Apr 09, 2018
3.31 is fine for towing and gets better fuel economy than 3.55. The 3.31 is mated with smaller tires than the 3.55 but the difference between the 275/70r18's and 275/65r20's is only 2.7%. If the 20 inch tire option was mated with a 3.40 gear ratio the engine rpm would be identical to 18" tires and 3.31 gears. So when the engine of the 3.31 equipped truck is turning 1400 rpm the engine of the 3.55 equipped truck with 20" wheels will be turning 1461 rpm if both trucks are traveling the same speed.
donn0128
Explorer II
Apr 09, 2018
Thats one of the reasons they put so many gears behind the newer motors. Choices. When you get to a climb, simply manually drop a gear or two to maintain the RPM in the power band.
alexleblanc
Explorer
Apr 09, 2018
I towed for 4 seasons with a 2013 F250 6.7 with the 3.31's, it worked fantastic and was decent on fuel. the only time I even wished for more gears was taking off from a dead stop trying to merge and even then it was quite good.
womps
Explorer
Apr 09, 2018
Pulled a 36 foot 5th wheel with a 2016 PS diesel and 3:55 gears. Pulled same load with 2017 PS diesel and 3:31 gears. Both 18 inch wheels and same size tires. 2017 had more power and torque on paper but I couldn’t tell the difference. Also didn’t notice any difference in rpm at cruising speed according to the tachometer.
LIKE2BUILD
Explorer
Apr 09, 2018
cliffy49 wrote:
Looking into....a 2012 F250 with a 6.7 and 3:31 gears.

I realize that 3:31s are not normally the ideal choice for towing but since this is a diesel, it may be different. I realize that 4:10s or 3:73s would be a better choice.

In previous truck generations when 3 or 4 speed transmissions were your only options, lowering the axle gear ratios was the only good way to increase applied torque to the wheels.

Newer transmissions with 6, 8, and 10 gears let the manufacturers reduce axle ratio for fuel efficiency and allows for using lower ratios on gears 1 & 2 to give you 'off the line' grunt even with a higher axle ratio. So, diesel or gas, the increased # of gears in the transmission makes up for the higher axle ratios.

KJ
dodge_guy
Explorer II
Apr 09, 2018
With the newer 6, 8 and 10 speed transmissions 3.30 and 3.55 gears are the norm. It will tow like a truck with 3.73’s.

No need to worry.
nohurry
Explorer
Apr 10, 2018
Lynnmor wrote:
Actually there is little choice and the gearing will be fine. 3.31 was used with 18" wheels and 3.55 was used with 20" wheels. The overall effect was the same with the engine turning the same RPM at the same speed. One exception is that the snow plow preparation package and the camper package had the 3.55 with 18" wheels. A diesel turns at a much lower RPM than a gas engine and you should not compare the gearing between the two. Now if you really want something to unnecessarily worry about, consider the fact that 5th gear is overdrive and 6th gear is over overdrive.

The 3:55's were available with 18" wheels if you added the camper package.

OP, you'll be fine. Plenty of torque, with the six speed will get er' done!
cliffy49
Explorer II
Apr 10, 2018
I want to thank every one for the comments regarding the question. Since I am new at RV'ing and have never even driven a diesel let alone owned one, just wanted to be sure about whether this would work or not.

Now too decide if this is the direction I want to go or maybe just look at a gasser. At least there I have a little more knowledge of what is needed.
4x4ord
Explorer III
Apr 10, 2018
If purchasing a diesel falls within your budget I think you should buy a diesel. A small trailer and a 1/2 ton would cost less to own.

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