2017 Chevrolet Silverado 3500HD Transmission & Axle Gear Ratios

Transmission gear ratios

The 2017 Chevrolet Silverado 3500HD was available with two primary transmission options: the 6L90 six-speed automatic for gasoline engines and the Allison 1000 six-speed automatic for the Duramax diesel.

6L90 (Gasoline Engines)

Allison 1000 (Duramax Diesel Engines)

Available axle ratios

The 2017 Silverado 3500HD offered a limited but effective range of axle ratios to cater to different demands.

How to identify your axle ratio

For Chevrolet trucks like the 2017 Silverado 3500HD, the easiest way to identify your vehicle's axle ratio is by checking the RPO (Regular Production Option) sticker. This sticker is typically located in the glove compartment or on the inside of the door jamb (driver's side). Look for a three-digit code that starts with "GT".

• GT4: Indicates a 3.73:1 axle ratio.
• GT5: Indicates a 4.10:1 axle ratio.

If the sticker is missing or unreadable, a visual inspection of the differential housing might reveal a metal tag bolted to it, which often lists the gear ratio. Alternatively, a Chevrolet dealership can provide the build sheet using your VIN.

Towing vs MPG impact

The choice of axle ratio significantly impacts both towing performance and fuel economy.

• Numerically Higher Ratios (e.g., 4.10:1): These ratios mean the engine completes more revolutions for every rotation of the wheels. This provides increased torque multiplication to the wheels, which is excellent for heavy-duty towing, accelerating with a substantial load, and off-road capability. However, the trade-off is higher engine RPMs at cruising speeds, leading to decreased fuel efficiency.
• Numerically Lower Ratios (e.g., 3.73:1): These ratios allow the engine to operate at lower RPMs at cruising speeds. This reduces fuel consumption and generally provides a quieter highway driving experience. While still capable of towing, a numerically lower ratio will provide less "pulling power" off the line compared to a higher ratio, making it less ideal for frequent maximum-capacity towing.

For the 2017 Silverado 3500HD, the 3.73:1 ratio provides a good balance for general hauling and daily driving, while the 4.10:1 ratio is strictly for those who prioritize maximum towing capability above all else.

Common issues

While the powertrains of the Silverado 3500HD are generally robust, some common issues can arise with differentials and transmissions:

• Ring and Pinion Whine: A persistent whining noise that changes with vehicle speed and load can indicate wear or improper setup of the ring and pinion gears within the differential. This often becomes more noticeable during deceleration or at specific speed ranges.
• Carrier Bearing Wear: The bearings that support the differential carrier can wear out, leading to growling or humming noises, especially around corners or when accelerating. If left unaddressed, this can lead to more significant differential damage.
• Limited-Slip Clutch Wear: For models equipped with a limited-slip differential, the internal clutches can wear over time. This may manifest as a chattering or shuddering sensation from the rear wheels during turns, especially at low speeds. Regular differential fluid changes with the correct friction modifier are crucial for these units.
• Allison 1000 Solenoid Issues: While generally very reliable, some Allison 1000 transmissions might experience occasional issues with internal solenoids, leading to harsh or delayed shifts. This is less common but can occur.

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