2019 Ford F-250 Super Duty Transmission & Axle Gear Ratios

Transmission gear ratios

The 2019 Ford F-250 Super Duty was available with two primary transmission options: the TorqShift-G 6-speed automatic transmission and the TorqShift 6-speed automatic transmission.

TorqShift-G 6-speed Automatic Transmission (6R100) — Gasoline Engines

TorqShift 6-speed Automatic Transmission (6R140) — Diesel & Heavy-Duty Gasoline

Both transmissions share the same gear ratios, however, the TorqShift 6R140 is a heavier-duty unit designed to handle the higher torque output of the diesel engine and for more demanding applications with the gasoline engine.

Available axle ratios

The 2019 F-250 Super Duty offered a range of axle ratios to cater to different needs, balancing towing capability and fuel economy.

Note: "Limited Slip" indicates a limited-slip differential, while "Open" refers to an open differential.

How to identify your axle ratio

Identifying your F-250's axle ratio is crucial for proper maintenance and upgrades. Here are the most common methods:

• Door-Jamb RPO Sticker: For Ford trucks, the door jamb sticker (typically found on the driver's side at the B-pillar) contains a wealth of information, including the axle code. Look for a two-character "AXLE" code. You'll then need to cross-reference this code with a Ford decode chart to determine the exact ratio and whether it's an open or limited-slip differential. For example, a code like "3L" would indicate a 3.73 limited-slip differential, while "37" might indicate a 3.73 open differential.

• Axle Tag: Many Ford axles have a metal tag attached to one of the differential cover bolts. This tag will often have the gear ratio stamped directly on it (e.g., "3 73" or "4 30"). Be aware that these tags can become corroded or go missing over time.

• VIN Decoder: You can use a Ford VIN decoder tool online (often available on enthusiast forums or parts websites) to get a detailed breakdown of your truck's original specifications, which usually includes the axle ratio.

Towing vs MPG impact

The choice of axle ratio has a significant impact on your truck's performance characteristics. It's a trade-off between towing capability and fuel efficiency:

• Numerically Lower Ratio (e.g., 3.31): A numerically lower axle ratio means the engine will spin fewer revolutions per minute (RPM) at a given road speed. This leads to better fuel economy, especially during highway cruising, as the engine isn't working as hard. However, it also reduces the mechanical advantage for towing, meaning the engine will have to work harder to get a heavy load moving and maintain speed, potentially leading to higher transmission temperatures and reduced towing capacity.

• Numerically Higher Ratio (e.g., 4.30): A numerically higher axle ratio means the engine will spin more RPMs at a given road speed. This provides a greater mechanical advantage, making it easier to tow heavy loads, especially from a standstill and on inclines. The increased RPMs, however, will generally result in lower fuel economy, particularly during highway driving.

For most F-250 owners who occasionally tow moderate loads, the 3.73 ratio offers a good balance. Those who frequently tow very heavy trailers or operate in challenging terrain might benefit from the 4.30 ratio with the gas engine, sacrificing some fuel economy for enhanced pulling power.

Common issues

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

• Ring & Pinion Whine: A persistent whining noise that increases with vehicle speed can indicate wear or improper setup of the ring and pinion gears. This often becomes noticeable between certain speed ranges or under acceleration/deceleration.

• Carrier Bearing Wear: The carrier bearings support the differential carrier within the axle housing. Worn carrier bearings can cause a rumbling or howling sound that changes with vehicle speed or when cornering. Ignoring this issue can lead to more severe damage to the differential.

• Limited-Slip Clutch Wear: If your F-250 is equipped with a limited-slip differential, the internal clutches can wear out over time. Symptoms include a chattering or binding sensation when turning, especially at low speeds, or a noticeable decrease in traction on slippery surfaces where both wheels should be receiving power. Regular differential fluid changes with the correct friction modifier are crucial for the longevity of limited-slip differentials.

Find a driveline shop on Repairius.