2021 Subaru Forester Transmission & Axle Gear Ratios

Transmission gear ratios

The 2021 Subaru Forester is exclusively offered with a continuously variable transmission (CVT), which Subaru refers to as Lineartronic. This transmission provides a wide range of ratios, offering both efficiency and responsive acceleration.

Available axle ratios

The 2021 Subaru Forester comes with a single axle ratio across all trims and configurations, designed to work optimally with its Lineartronic CVT and Boxer engine.

How to identify your axle ratio

Unlike some vehicles that offer multiple axle ratios, the 2021 Subaru Forester simplifies identification as all models come with a 3.700 final drive ratio. Therefore, you won't find a specific RPO code for the axle ratio on a door jamb sticker, nor will there be an axle tag to decipher a different ratio. If you ever needed to confirm this, a Subaru dealership service department could provide this information based on your VIN.

Towing vs MPG impact

For the 2021 Subaru Forester, the impact of axle ratio on towing versus MPG is not a variable you need to consider at the time of purchase, as all models share the same 3.700 final drive ratio. However, understanding the general principle is still valuable.

A numerically lower axle ratio (e.g., 3.08) means the engine will spin fewer revolutions per minute (RPM) at a given road speed. This generally translates to better fuel economy on the highway because the engine is operating less intensely. However, it also means less torque multiplication to the wheels, which can make the vehicle feel less responsive during acceleration and reduce its towing capability.

Conversely, a numerically higher axle ratio (e.g., 4.10) causes the engine to spin at higher RPMs for the same road speed. This increases torque multiplication, improving off-the-line acceleration and enhancing towing capacity. The trade-off is typically a reduction in fuel economy, especially at highway speeds, as the engine is working harder.

Subaru engineers have selected the 3.700 ratio for the Forester to strike an optimal balance between fuel efficiency, everyday drivability, and its modest towing capacity. This ratio, combined with the wide range of the Lineartronic CVT, allows the Forester to deliver a good blend of both worlds without the need for multiple axle options.

Common issues

While the Subaru Forester powertrain is generally reliable, some common issues can occasionally arise in the driveline. These are not necessarily unique to the 2021 model year but can be pertinent to vehicles with similar setups:

• CVT anomalies: While robust, some owners occasionally report minor issues with CVTs, such as occasional hesitation or unusual noises. Regular fluid changes are crucial for CVT longevity.
• Rear Differential Noise: Over time and mileage, some rear differentials can develop a whine, especially during acceleration or deceleration. This can be caused by worn bearings, improper gear mesh, or low fluid levels. Addressing this early is important to prevent more significant damage.
• Carrier Bearing Wear: The carrier bearing, which supports the driveshaft, can wear out, leading to vibrations or clunking noises, particularly noticeable when shifting into gear or accelerating from a stop. This is more common in higher-mileage vehicles.
• Limited-Slip Clutch Pack Wear (if applicable): If equipped with a limited-slip differential (LSD) in specific markets or trims (though less common in mainstream Forester models), the clutch packs can wear, leading to a loss of limited-slip function or chattering noises during turns. Regular fluid changes with the correct friction modifiers are essential for LSD-equipped differentials.

Routine maintenance, including timely fluid changes for both the CVT and differentials, is the best way to prevent many of these potential issues and ensure the longevity of your Forester's powertrain.

Find a driveline shop on Repairius.