2015 Ford F-150: Transmission & Axle Gear Ratios

Transmission Gear Ratios

The 2015 Ford F-150 was available with one primary automatic transmission, the 6-speed 6R80.

6-Speed Automatic (6R80)

Available Axle Ratios

Ford offered a variety of axle ratios for the 2015 F-150, allowing buyers to prioritize either fuel economy or towing/hauling performance. The availability of these ratios was often tied to specific engines, trim levels, or optional packages like the Max Trailer Tow Package.

How to Identify Your Axle Ratio

Knowing your truck's specific axle ratio is crucial for ordering the correct parts or understanding its performance characteristics. Ford provides a couple of straightforward ways to find this information.

Door Jamb Sticker

The easiest method is to check the Safety Compliance Certification Label, located on the driver's side door jamb. Look for the "AXLE" code listed on the sticker. This two-digit code corresponds to a specific ratio.

• 15: 3.15 Non-Limited Slip
• 27: 3.31 Non-Limited Slip
• L9: 3.55 Electronic Locking
• 26: 3.55 Non-Limited Slip
• L3: 3.73 Electronic Locking
• 25: 3.73 Non-Limited Slip

Axle Tag

If the door jamb sticker is missing or unreadable, you can find the information on a tag bolted to the differential housing itself. The tag will have a series of numbers. If you see a sequence like "3 31," it indicates a 3.31 ratio. If you see "3L31," it signifies a 3.31 ratio with a limited-slip differential.

Towing vs. MPG Impact

The axle ratio has a direct and significant impact on both fuel economy and towing capability. The number represents how many times the driveshaft turns for every one rotation of the wheels.

• Numerically Lower Ratios (e.g., 3.15, 3.31): These are often called "taller" gears. The engine turns at a lower RPM at highway speeds, which reduces fuel consumption. This is ideal for drivers who spend most of their time on the highway and do minimal towing. The trade-off is reduced pulling power off the line.

• Numerically Higher Ratios (e.g., 3.73): Referred to as "shorter" gears, these ratios provide more torque to the wheels, making it easier to pull heavy loads from a standstill. This is the preferred choice for towing. However, the engine must run at a higher RPM on the highway, which leads to lower fuel economy.

• Balanced Ratios (e.g., 3.55): This ratio is a popular compromise, offering a good blend of decent towing and hauling capability without a severe penalty to fuel economy, making it a great all-around choice for many F-150 owners.

Common Issues

While the 2015 F-150 driveline is generally robust, some issues can arise, particularly as the miles add up.

• Pinion Bearing Whine: A high-pitched whining noise that changes with vehicle speed is a classic symptom of a worn pinion bearing. The noise is often most noticeable during deceleration.
• Carrier Bearing Failure: The carrier bearings support the differential carrier within the axle housing. Failure can lead to a rumbling or growling noise that changes pitch with speed.
• Limited-Slip Clutch Wear: On models equipped with a limited-slip differential, the internal clutches can wear out over time. This typically presents as a chattering or binding sensation when turning slowly, such as in a parking lot. A fluid change with the correct friction modifier often resolves this, but eventual replacement may be necessary.

If you're experiencing any of these driveline issues, it's best to have your truck inspected by a qualified technician.

Find a driveline shop on Repairius.