2020 Ford F-350 Super Duty Transmission & Axle Gear Ratios

Transmission gear ratios

For the 2020 model year, the Ford F-350 Super Duty was offered with two transmission options: the TorqShift G 10-speed automatic and the TorqShift 6-speed automatic. The 10-speed was paired with the 6.7L Power Stroke diesel and the 7.3L Godzilla gas engine, while the 6-speed was used with the 6.2L Boss gas engine.

TorqShift G 10-speed Automatic (10R140)

TorqShift 6-speed Automatic (6R140)

Available axle ratios

The 2020 Ford F-350 Super Duty offered a range of axle ratios to cater to various needs, from heavy-duty towing to improved fuel economy. The availability of certain ratios was dependent on the engine, trim level, and specific packages.

How to identify your axle ratio

Identifying your F-350's axle ratio is crucial for proper maintenance and modifications. For Ford trucks, the most reliable place to find this information is on the door-jamb sticker, usually located on the driver's side. Look for a section labeled "AXLE" or "AXLE CODE." The code will correspond to one of the ratios listed above. For example, "3L" indicates a 3.31:1 electronic locking differential, while "3H" signifies a 3.55:1 limited-slip differential. In some cases, especially on older models or if the sticker is damaged, you might find an axle tag bolted to one of the differential cover bolts. This metal tag will usually have the gear ratio stamped on it.

Towing vs MPG impact

Understanding the relationship between axle ratio, towing capability, and fuel economy is essential for F-350 owners. A numerically lower axle ratio (e.g., 3.31:1) means the engine will run at lower RPMs at a given road speed. This generally translates to better fuel economy, especially during highway cruising, as the engine isn't working as hard. However, a lower ratio reduces the mechanical advantage for towing, meaning the engine will have to work harder, potentially increasing transmission temperatures and reducing overall towing capacity.

Conversely, a numerically higher axle ratio (e.g., 4.30:1) provides a greater mechanical advantage. This allows the engine to more easily move heavier loads and accelerate more quickly, making it ideal for frequent or heavy towing. The trade-off, however, is that the engine will operate at higher RPMs at cruising speeds, leading to decreased fuel efficiency. A balanced ratio like 3.55:1 or 3.73:1 attempts to strike a compromise between these two extremes, offering acceptable towing performance without severely impacting fuel economy for most users.

Common issues

While the Ford Super Duty axles are generally robust, some common issues can arise:

• Ring and Pinion Whine: A notorious issue that can manifest as a howling or whining noise, particularly noticeable at certain speeds or under deceleration. This is often caused by incorrect gear mesh, worn gears, or improper bearing pre-load. Ignoring it can lead to catastrophic failure.
• Carrier Bearing Wear: The carrier bearings support the differential carrier within the axle housing. Over time, especially with heavy loads or aggressive driving, these bearings can wear out, leading to noise, vibration, and eventually differential damage.
• Limited-Slip Clutch Pack Wear: For vehicles equipped with a limited-slip differential, the clutch packs can wear out. This results in the differential acting more like an open differential, reducing traction in low-grip situations. Signs include a noticeable lack of traction from one wheel during slippage or a chattering noise from the rear end when cornering at low speeds.

Regular differential fluid changes and inspections can help mitigate these issues and prolong the life of your F-350's driveline components.

Find a driveline shop on Repairius.