Axle Issues to Consider
One tricky thing about choosing an axle ratio is that the EPA fuel economy information on the window sticker primarily applies to the "base" or standard axle ratio, even though that particular truck might come with an optional axle ratio, says Dan Edmunds, director of vehicle testing for Edmunds. Therefore, any axle ratio you see listed on the options side of the window sticker will lower the fuel economy figures printed on the very same sticker.
Another difficulty is that optional axle ratios, and their effects on towing, cannot be compared across truck manufacturers, Dan Edmunds says. That's because each truckmaker may use a different tire size, and the tire itself acts as the final "gear" in the system. It's best to compare the axle options within a single brand to see how each one affects the tow ratings listed in that brand's towing guide, he says.
As you shop for your truck, you might hear axle ratios with lower numbers referred to as being "tall" gears and those with higher numbers as "short" gears. To more easily remember what this means, think of a tall person who travels a greater distance with each step. Similarly, a tall gear moves the truck farther with each turn of the engine. Trucks with tall gears deliver better gas mileage because their engines turn fewer rpm at a given road speed. But taller gears also reduce the torque — or power — so you can't tow heavier trailers or haul heavier loads.
Ram and other manufacturers recommend that truck shoppers look at the towing and payload tables on their websites. They're there to help customers select the right powertrain for their specific needs. As truck manufacturers produce transmissions using more gears, the axle ratios will also change. For example, a transmission with more gears might allow a truckmaker to offer a taller rear axle ratio (a 3.55 instead of 3.73) and still provide improved towing and hauling capabilities.
Before you leave for the dealership, take a moment to think about how you're going to use the truck. When in doubt, default to a higher numerical axle ratio. While it will lower your fuel economy slightly, it will also mean you will be more comfortable while hauling and towing over long distances.
But if your concern is getting better fuel economy at highway speeds, a numerically lower drive-axle ratio might be right for you, as could a transmission with more gears.