otrfun wrote:
Take a look at the 2014-2018 Ram tow capacity ratings for the 3.42, 3.73, or 4.10 rear ends.
There can be as much as a 8,000 - 9,000 lb. difference between a 3.42 and 4.10 rear end (same make and model truck).
These tow capacity ratings DIRECTLY define the relative difference in the amount of driveline stress a 3.42, 3.73, and 4.10 rear end can sustain.
Most folks I know would easily define a 8,000 - 9,000 lb. difference as "significant".
I'd say a major factor is startability, i.e. the steepest grade you can start a load on. Since 1st gear is fixed, the towing limit goes up with a lower rear end.
Once at speed, i.e. the gradeability, is pretty much equal with modern 8 / 10 speed transmissions (Ram's 6 spd might be more limiting).
In other words, very little difference pulling mountain grades between a 3.42 and 4.10, with 8 / 10 spd transmissions. You'll simply be in a lower gear.
The "stress" in front of the transmission input shaft would be identical (determined solely by engine output). The driveshaft would be under slightly higher torque on the 3.42 truck, as it's in a lower gear, but way below what it experiences in 1st gear. The axle shafts would be very similar (takes a constant axle torque to pull xxx lbs up xx% grade).
If we had perfect CVTs, then a 3.42 truck and 4.88 truck would pull the grade at the exact same speed, down to the decimal point.
