Properly spec’ing your heavy-duty truck means considering every element of your duty cycle, not just the engine and transmission. One of the most critical decisions is selecting the axle ratio, with the key factor between a 6×2 and 6×4 axle configuration almost always being the type of terrain on which a vehicle will operate.
To make sure we’re all on the same page, let’s define the difference between 6×2 and 6×4. In a 6×2 configuration, only one of the two rear axles receives power. In a 6×4, both of the tractor’s rear axles are drive axles. Historically, many drivers prefer the 6×4 configuration, but 6x2s are garnering new attention as fleet managers and owner-operators look to optimize performance.
If the truck will operate primarily on well-maintained, paved roads with moderate grades, 6×2 is likely your best bet, especially if you hope to maximize fuel economy. Fewer drive axles produce less rolling resistance, improving fuel efficiency by an average of about 2.5 percent compared with that of a 6×4. That’s big savings in your pocket over time.
The 6×2 also offers reduced weight for drivers looking to haul heavier payloads and is ideal for consistent line-haul operation with few slippery or icy road conditions. However, the 6×4 is preferred if you expect to regularly operate off-highway or in bad weather where traction is really put to the test.
The 6×4 configuration is ideal for those who need to deliver power to more tires, producing better control and overall vehicle operation. As a popular axle configuration, 6x4s also tend to maintain better resale value.
The biggest concern expressed when considering a 6×2 configuration is reduced traction, but these concerns can be overcome by using load shifting techniques to increase weight on the drive axles at low speeds or by using traction control and automated load transfer systems.
If you’re spec’ing your truck with a typical direct-drive transmission, a faster axle ratio for downspeeding and/or using single wide-base tires, a 6×2 configuration is probably the way to go. If you prefer a vehicle with better traction and spend a significant time in off-highway or inclement weather conditions, you should probably opt for a 6×4 configuration.
Whatever axle configuration you choose, be sure to ask your heavy-duty truck dealer about all the options available to you. Properly spec’ing your truck from the start contributes to years of happy driving.