2017 Chevrolet Silverado 1500: Transmission & Axle Gear Ratios

Understanding the powertrain of your 2017 Chevrolet Silverado 1500 is key to maximizing its performance, whether you prioritize towing capability, fuel efficiency, or a balance of both. The combination of your transmission and rear axle gear ratio dictates how your truck puts power to the pavement. This guide covers the specific gear ratios available for the 2017 model year, how to identify what your truck is equipped with, and what it all means for your driving experience.

Transmission Gear Ratios

In 2017, the Silverado 1500 was available with two excellent automatic transmissions: the Hydra-Matic 6L80 6-speed and the more advanced Hydra-Matic 8L90 8-speed. The 6-speed was typically paired with the 4.3L V6 and was standard on lower-trim 5.3L V8 models. The 8-speed transmission was standard on LTZ and High Country trims with the 5.3L V8 and was paired exclusively with the powerful 6.2L V8 engine.

6-Speed Automatic (6L80)

8-Speed Automatic (8L90)

Available Axle Ratios

The axle ratio represents the number of times the driveshaft must turn for the wheels to make one full rotation. It acts as the final stage of torque multiplication. A higher numerical ratio (like 3.73) provides more torque to the wheels for better acceleration and towing power, while a lower numerical ratio (like 3.08) keeps engine RPMs down for better highway fuel economy.

How To Identify Your Axle Ratio

Identifying the specific axle ratio in your Silverado is straightforward. Unlike some manufacturers that require checking a tag on the differential itself, GM makes it easy by listing all Regular Production Option (RPO) codes on a sticker inside the vehicle.

1. Check the RPO Sticker: Open the driver's side door and look in the glove box. You will find a silver sticker labeled "Service Parts Identification."
2. Find the "G" Codes: This sticker contains a long list of three-character codes. Scan the list for codes that start with "G." The codes listed in the table above (GU4, GU5, GU6, GT4) will tell you exactly which ratio your truck left the factory with. You will also find the RPO code G80, which indicates your truck is equipped with the popular Eaton automatic locking rear differential.
3. VIN Decoder: If the sticker is missing or illegible, you can use an online VIN decoder service. While many services can provide this information, it may not be as consistently accurate as checking the RPO sticker directly.

Towing vs. MPG Impact

The trade-off between power and efficiency is directly managed by the axle ratio.

• Numerically Lower Ratios (3.08, 3.23): These are considered "taller" gears. They allow the engine to operate at a lower RPM at highway speeds, reducing fuel consumption. This makes them ideal for drivers who spend most of their time on the highway or do very little towing. The downside is less off-the-line acceleration and a lower maximum tow rating.

• Numerically Higher Ratios (3.42, 3.73): These are "shorter" gears. They multiply the engine's torque more effectively, resulting in quicker acceleration and significantly improved towing and hauling performance. The 3.73 ratio, found in the Max Trailering Package, is essential for achieving the Silverado's highest tow ratings. The trade-off is higher engine RPM at cruising speeds, which leads to a decrease in overall fuel economy.

Common Issues

While the 2017 Silverado 1500 has a generally reliable driveline, a few issues are known to occur.

• Transmission Shudder (8-Speed): Some owners of trucks with the 8L90 transmission have reported a shudder or vibration, particularly under light acceleration. This issue has often been traced to the original-fill transmission fluid or the torque converter. A fluid flush with an updated Mobil 1 synthetic fluid often resolves the problem.
• Pinion Seal Leaks: A leak from where the driveshaft enters the differential is a common issue on many trucks. This is caused by a failing pinion seal and is identifiable by gear oil residue on the front of the differential housing. It should be replaced to prevent loss of gear oil and subsequent damage.
• G80 Locker Wear: The G80 automatic locking differential is a strong point for GM trucks, but it can wear over time. You might notice it failing to engage in low-traction situations or making clicking noises. Its clutch-based mechanism can wear, especially with aggressive use or oversized tires.

Whether you're looking to service a worn-out component or considering a gear ratio swap to better suit your needs, expert help is recommended.

Find a driveline shop on Repairius.