3:31 Gearing
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 realiz...
Forum Discussion
Lynnmor wrote:4x4ord wrote:
A lower geared truck does not tow better than a properly geared truck. For example if a 3.31 axle ratio can tow a 15000 lb trailer up a hill at 75 mph at wide open throttle It will be out doing a 3.55 equipped truck that is otherwise identical towing the same 15000 lb trailer up that same hill.
Now that does not make sense.
The truck in question has no real options. The two gear ratios available are very close and factoring in tire size there is virtually no difference. While some rail against the gear ratio available, there is absolutely no issue and folks need to understand that the 6.7 diesel will pull just fine as designed.
While I am pulling not much more than half the maximum tow rating, I top many of PA's finest four lane hills without dropping out of 6th gear.
Not dropping out of 6th gear is not the goal. Matching gear ratios to load to HP and expected incline is what the engineers do. The overdrive gears are intended to be used for economy .... cruising while high power is not required. Hit a 6% grade on the highway and if you have the right gears you should be in 4th gear.
The difference in engine rpm while traveling 60 mph between a 3.31 equipped truck and a 3.55 equipped truck with 20" wheels is a little over 4%. The 3.55 truck runs 2520 in 4th gear and 60 mph and the 3.31 equipped truck runs 2415.
So if the 3.31 truck is pulling at maximum power (2900 rpm) it will be traveling 72 mph in 4th gear. The 3.55 equipped truck will only be traveling 69 mph. If the 3.55 truck were to up shift to 5th its engine's rpm would drop to 2170 rpm and the truck would slow down.
So the lower speed gear ratio is not always going to out pull the higher speed ratio truck.
