2015 Ford F-250 Super Duty Transmission & Axle Gear Ratios

Transmission gear ratios

The 2015 Ford F-250 Super Duty was offered with a single transmission option, the TorqShift 6R140 automatic transmission, regardless of engine choice.

Available axle ratios

The 2015 F-250 Super Duty offered a variety of axle ratios to cater to different needs, from improved fuel economy to maximum towing capability. The availability often depended on the engine and trim level.

How to identify your axle ratio

For Ford trucks like the 2015 F-250 Super Duty, the axle code is typically found on the driver's side door jamb sticker. Look for a label that contains "AXLE" or "AXLE CODE." The code will be a two-digit alphanumeric code. You can then cross-reference this code with a Ford axle code chart (which can be found online or at a dealership) to determine your specific ratio and whether it's a limited-slip or open differential.

Alternatively, some Ford axles have a metal tag attached to one of the differential cover bolts. This tag will often have the axle ratio stamped directly on it. However, these tags can become corroded or go missing over time.

If neither of these methods yields the information, a Ford dealership can typically decode your VIN to provide the original build specifications, including the axle ratio.

Towing vs MPG impact

The axle ratio plays a significant role in determining a truck's performance characteristics, particularly concerning towing capability and fuel economy.

• Numerically lower ratios (e.g., 3.31:1, 3.55:1): These ratios equate to fewer rotations of the driveshaft per rotation of the wheel. This results in lower engine RPMs at highway speeds, which generally translates to better fuel economy. However, with less mechanical advantage, the engine has to work harder to get the vehicle moving or to tow heavy loads, which can negatively impact towing performance and strain the powertrain.

• Numerically higher ratios (e.g., 3.73:1, 4.10:1): These ratios mean more rotations of the driveshaft per wheel revolution. This provides a greater mechanical advantage, allowing the engine to accelerate the vehicle and tow heavy loads more easily. The trade-off is higher engine RPMs at cruising speeds, leading to decreased fuel economy. Trucks equipped with higher axle ratios are typically preferred for frequent heavy towing or demanding off-road applications.

Choosing the right axle ratio is a balance between your primary use case. If you primarily use your F-250 for daily driving and occasional light hauling, a lower numerical ratio might be more appropriate. If you regularly tow heavy trailers or navigate challenging terrain, a higher numerical ratio would be more beneficial.

Common issues

While the Ford F-250 Super Duty and its components are generally robust, certain issues related to the driveline can arise over time, especially with neglect or heavy use:

• Ring and Pinion Whine: A common sign of worn or improperly set up ring and pinion gears is a distinct howling or whining noise that changes with vehicle speed and load. This can be caused by improper gear mesh, worn bearings, or insufficient lubrication.

• Carrier Bearing Wear: The carrier bearings support the differential carrier within the axle housing. Worn carrier bearings can lead to noise (a growling or rumbling sound), vibration, and eventually significant damage to the differential. This is often exacerbated by heavy towing or off-road use without proper maintenance.

• Limited-Slip Clutch Wear: Many F-250s were equipped with limited-slip differentials. Over time, the clutch packs within these differentials can wear out, leading to a loss of limited-slip functionality (meaning one wheel can spin freely while the other has no power). This can be indicated by a chattering or binding sensation during tight turns, especially when starting from a stop.

Regular maintenance, including differential fluid changes at recommended intervals, can significantly extend the life of your F-250's driveline components.

Find a driveline shop on Repairius.