The regular posting of 4.10 and 4.56 questions in Dodge forums is proof that the Ram needs a 6 speed automatic with numerically higher 1st, 2nd, 3rd gears that give performance, and lower ratio 4, 5, 6 gears that give 3.21 like fuel economy. A durable 7 speed auto would be even better.

 

an old post that might be of interest:
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Thanks for posting that guido7.

I have been filling in the specs for 3rd gen 5.7Hemi Rams
in a software program called 'Fuel Economy Calculator'
and was interested in what it would say
with 4.56 gears versus the standard diffs of 3.55 or 3.73

At 71 mph the program predicted 16.57 MPG at 2306 rpm
which matches your experience
and estimated that the engine was at 52% load
and had 48% of maximum torque in reserve for passing or climbing hills.
With this 48% reserve torque the engine could take the truck up a 5.7% grade
hill
(which is fairly steep) without downshifting.

With 3.92 diff gears the program predicts
at 71 mph the MPG would improve to 17.07 at 1983 rpm
and estimated the engine was at 61% load.
With 39% reserve torque the engine could take the truck up a 3.9% grade hill
without downshifting

With 3.73 diff gears the program predicts
at 71 mph the MPG would improve to 17.16 at 1883 rpm
and the estimated engine load was 65%
With 35% reserve torque the engine could take the truck up a 3.2% hill
without downshifting.

With 3.55 diff gears the program predicts
at 71 mph the MPG would improve to 17.22 at 1796 rpm
and the estimated engine load was 70%
With 30% reserve torque the engine could take the truck up a 2.6% hill
without downshifting (most gentle interstate hills are less than 2%)

With 3.21 diff gears the program predicts
at 71 mph the MPG would decrease to 16.19 at 1624 rpm
and the estimated engine load was 80%
which is into the 'fuel enrichment mode' to prevent pinging
where the air to fuel ratio is richened from normal 14.7 down to 11
With 20% reserve torque the engine could take the truck up a 1.5% grade
without downshifting.

This is not to say that 3.21 diff gears cannot improve MPG
under the right conditions.

For example the 3rd Gen Rams (Cd=0.528 and 35.1 sq feet) are
quite a bit blunter and less aerodynamic
than the 2nd Gen Rams (Cd=0.44 and 34.49 sq feet).
If the aerodynamics of the new Rams could be made as good as the
older 1994-2001 Rams then:

The program predicts with 3.21 diff gears, 5.7 Hemi and 1994 aero specs
at 71 mph the MPG would be 19.51 at 1624 rpm
and the engine load would be 70%
and the engine could pull the better aero truck up a 2.3% grade without
downshifting.

DaimlerChrysler recently showed off a high MPG show car called the 'BoxFish'
that imitated the shape of a fish to get the a 'realworld' Cd of 0.19
{the real fish is even better at Cd=0.10}

If a 3rd Gen Ram had the aerodynamic Cd of the BoxFish show car
and its present 35.1 square feet of frontal area
the program predicts
at 71 mph with 2.73 diff gears the MPG would be 28.55 at 1381 rpm
and the engine load would be 57%
with 43% reserve torque at this low rpm
the engine could pull a 2.5% grade hill with downshifting.

 

What would be the predictions for 4.10 gears ?

 

about half way
between 4.56 and 3.92
in the predictions above