Axle ratio

[MT755]

The truck they use for the mpg on the 3.0 hurricane SO test is the 3.21. How much mpg's do we lose with the 3.55 or 3.92. The HO hs the 3.92 as it's only available ratio. It's rated 3 mpg less than the SO. How much better would the HO get with the 3.21 ratio? I don't understand why they all don't have the 3.21. The truck has 8 speeds, it doesn't need the 3.92 gears or 3.55 gears. The transmission locks the torque converter in all gears. It's not like the old 4 speeds.

 

[Ripper]

I specifically got one with the 3.92 because I tow. I looked at a bunch of trucks and didn't see any with the 3.21

 

[NorskieRider]

From what I've read, the 3.92 helps with getting a heavy load moving, after that the transmission just picks the right gear and it's a moot point.
Since the HO is rated to tow less than the SO I'm going to guess that the 3.92 being mandatory on the HO is all about off-the-line acceleration and fitting larger tires.

 

[Ripper]

From what I've read, the 3.92 helps with getting a heavy load moving

This is important when you are starting from a dead stop on a grade and you're towing 8-10k pounds.

 

[Grimlakin]

I am running 3.55 with the SO and averaging around 19.2 mpg mixed heavy towards highway.