2020 GMC Acadia Transmission & Axle Gear Ratios

Transmission gear ratios

The 2020 GMC Acadia offered a few different transmission options, each with its own set of gear ratios. Understanding these ratios is crucial for comprehending how your Acadia performs in various driving conditions, from city commuting to towing.

9-Speed Automatic (M3H / M3N)

This transmission was paired with the 2.0L turbocharged 4-cylinder and the 3.6L V6 engines, providing a wide range of gears for optimal performance and fuel efficiency.

6-Speed Automatic (M3V)

This transmission was standard with the 2.5L 4-cylinder engine.

Available axle ratios

The axle ratio plays a significant role in how your Acadia applies power to the wheels. A numerically higher ratio provides more torque for towing, while a numerically lower ratio generally improves fuel economy.

Note: The 2020 GMC Acadia primarily utilized a single axle ratio across its configurations, which is integrated with the transmission. The effective final drive ratio is what truly dictates performance and fuel economy.

How to identify your axle ratio

For most GM vehicles, including the 2020 GMC Acadia, you can identify your vehicle's axle ratio by checking the RPO (Regular Production Option) sticker. This sticker is typically found in the glove box or on the door jamb of the driver's side. Look for a three-digit code that corresponds to the axle ratio. Common RPO codes for axle ratios might include "GUx" followed by a number, though for the 2020 Acadia, as noted above, a single ratio was generally standard. If you can't find the sticker or decipher the codes, a GM dealership can provide this information using your VIN.

Towing vs MPG impact

The relationship between axle ratio, towing capacity, and fuel economy is straightforward:

• Numerically Lower Axle Ratio (e.g., 3.08): This means the engine has to spin fewer times for each revolution of the wheels. The result is generally better fuel economy on the highway, as the engine operates at lower RPMs. However, it also means less torque multiplication, which can reduce towing capability and acceleration.
• Numerically Higher Axle Ratio (e.g., 4.10): With a higher ratio, the engine spins more times for each wheel revolution. This provides greater torque multiplication, leading to improved acceleration and significantly enhanced towing capacity, especially for heavy loads. The trade-off is often reduced fuel economy, as the engine operates at higher RPMs, particularly at highway speeds.

For the 2020 GMC Acadia, with its generally standardized final drive ratio, the impact of axle ratio choices on towing versus MPG is less about choosing different physical axle ratios and more about the overall powertrain tuning. The 3.49 ratio offers a balanced approach, providing adequate towing capabilities for a mid-size SUV while maintaining reasonable fuel efficiency.

Common issues

While the 2020 GMC Acadia's driveline components are generally robust, some issues can arise over time with any vehicle:

• Ring & Pinion Whine: A persistent whining noise that changes with vehicle speed (but not necessarily engine RPM) can indicate wear in the ring and pinion gears within the differential. This often becomes more noticeable during acceleration or deceleration.
• Carrier Bearing Wear: The carrier bearings support the differential carrier. If these bearings wear out, they can produce a humming or rumbling noise, particularly at certain speeds.
• Limited-Slip Clutch Wear (if equipped): If your Acadia is equipped with a limited-slip differential, the clutch packs within it can wear down over time. This might manifest as clunking or chatter, especially during tight turns at low speeds. However, many Acadia models feature open differentials or electronic traction control systems that mimic limited-slip functionality, which have different wear characteristics.

Regular differential fluid changes (if applicable based on your vehicle's maintenance schedule and type of differential) can help prevent premature wear and extend the life of these components.

Find a driveline shop on Repairius.