[HankL]

If you look at a "completely stock" 5.7 Hemi 4x4
a 3.55 differential in 0.67 top gears puts the
best engine fuel efficiency in terms of converting
a pound of fuel into hours of horsepower
right near 65 mph.

In a similar way
a 3.73 differential puts the optimum
right near 77 mph.

If you think about those numbers
that is exactly what you expect a Dodge engineer to do
for the 'average customer'.

You can also work out where the best engine efficiency
is for towing a 5000 pound trailer in 1.00 third gear
and you get around 60 mph - which also makes sense.

If a Ram owner 'improves' his truck by adding a tonneau for aero improvement
of low rolling resistance tires, or swapping in an electric fan,
then he could drop to a numerically lower gear ratio.

If a Ram owner puts an added 'strain' on the truck by putting on wide aggressive tread 'mudder' tires that roll with more resistance, or adds a 'bug deflector' or light bar that has wind drag then he would need a numerically higher gear ratio.

I read many posts from fuzzy thinkers who say things like:
"It's a truck so you shouldn't even care about MPG"

I am thankful those people don't handle my checking account.

It is the vehicles that use a lot of fuel
- trucks, airplanes, boats
that can save the most money from small changes in efficiency.

Walmart has recently announced
that the best way to improve profits
is to change its trucks so that they go
from just below 7 MPG (already good by 18 wheeler standards)
to 12 MPG.
That is going to be a tough job but Walmart says they are willing to spend a lot of money on Research and Development to make it happen.