2017 Ford F-250 Super Duty: Transmission & Axle Gear Ratios

Transmission Gear Ratios

The 2017 Ford F-250 Super Duty was offered with two different six-speed automatic transmissions, both engineered for heavy-duty use. The transmission installed in your truck depends on the engine it's equipped with.

TorqShift-G 6-Speed Automatic (6R100)

This transmission was paired exclusively with the 6.2L V8 gasoline engine.

TorqShift 6-Speed Automatic (6R140)

This heavy-duty transmission was the sole option for trucks equipped with the powerful 6.7L Power Stroke V8 turbo diesel engine.

Available Axle Ratios

Ford offered a range of rear axle ratios for the 2017 F-250, allowing buyers to tailor the truck's performance to their specific needs, whether that was maximizing fuel economy or enhancing towing capability.

Note: Axle codes ending in "L" or "N" typically denote an electronic locking differential, while others may be conventional or limited-slip.

How to Identify Your Axle Ratio

Knowing your truck's specific axle ratio is crucial for ordering parts or understanding its towing potential. There are two primary methods for identifying it on your F-250:

1. Safety Compliance Certification Label: The easiest method is to check the sticker on your driver's side door jamb. Look for the "AXLE" code listed on the sticker. This two-character code (e.g., 3L, 4N) directly corresponds to the ratio installed at the factory.

2. Axle Differential Tag: For those who prefer to get under the truck, a metal tag is bolted to the differential cover. This tag has the gear ratio stamped directly onto it (e.g., "3 73" for a 3.73 ratio or "3L73" for a 3.73 with a locking differential). Over time, this tag can become caked with dirt or rust, so it may require some cleaning to be legible.

If the sticker is missing or the tag is unreadable, a Ford dealership can decode your VIN to provide the original factory specifications.

Towing vs. MPG Impact

The axle ratio is a multiplier for the torque produced by the engine and transmission. The trade-off between power and efficiency is directly tied to this gearing.

• Numerically Higher Ratios (e.g., 4.30): These ratios are known as "shorter" gears. They multiply engine torque more effectively, making it easier to get a heavy load moving from a standstill. This significantly improves towing and hauling performance, especially when climbing grades. The downside is that the engine must run at a higher RPM at any given speed, which leads to increased fuel consumption.

• Numerically Lower Ratios (e.g., 3.31): Referred to as "taller" gears, these ratios don't multiply torque as much. This requires the engine to work harder to get a very heavy load moving. However, once at cruising speed on the highway, the engine can operate at a much lower RPM. This "lugging" effect is ideal for maximizing fuel economy in unloaded or lightly loaded conditions.

A balanced ratio like 3.73 is the most common because it offers a good compromise, providing respectable towing ability without a severe penalty to everyday fuel efficiency.

Common Issues

While the Sterling axles used in the F-250 are generally robust, a few issues can arise, particularly in high-mileage or hard-working trucks.

• Pinion Bearing Whine: A high-pitched whining noise that changes with vehicle speed (not engine RPM) is a classic symptom of a worn pinion bearing. It's often most noticeable during deceleration.
• Carrier Bearing Noise: A rumbling or grinding noise that is present when driving, especially during acceleration, can point to failing carrier bearings that support the differential internally.
• Leaking Pinion or Axle Seals: Wetness or drips around the front of the differential (pinion seal) or at the ends of the axle tubes (axle seals) are common signs of aging seals that need replacement.

Addressing these driveline issues promptly is key to preventing a more catastrophic and expensive failure down the road.

Find a driveline shop on Repairius.