Let’s talk matching axle spec to load demands.
When it comes to handling maximum, constant and/or diminishing loads, axle spec choices can be influenced by the amount of time spent in each load situation.
Startability and gradeability come into play when discussing load situations. The more time your trucks spend in a maximum load situation may impact startability and gradeability to a greater degree than if the majority of time is spent in a constant load or diminished load situation.
A direct-drive transmission paired with a fast axle ratio like a 2.28 may be perfect for fuel savings. But if your trucks roll through mountain roads or uses the truck less than 80% 85% in the top two gears in a line-haul application, then the 2.28 may not be ideal and actually hurt your fuel economy.
Conversely, an overdrive ratio like a 3.42 or 3.08 may give the same fuel savings as a direct drive in the top two gears and not have to worry about startability or gradeability.
The effect of maximum, constant and/or diminishing loads affect on axle specs is also impacted by your axle configuration. Are you running a tandem or a single axle? And what type of engine and transmission and load are the trucks carrying?
These are the questions you need to answer when you sit down to spec your next truck to ensure your axles can tackle your specific application.