2019 Chevrolet Silverado 3500HD Transmission & Axle Gear Ratios

Transmission gear ratios

The 2019 Chevrolet Silverado 3500HD was available with two primary transmission options: the 6L90 6-speed automatic and the new-for-2019, heavy-duty 10L1000 (also known as the Allison 10-speed) automatic transmission.

Hydra-Matic 6L90 (6-speed automatic)

Allison 10L1000 (10-speed automatic)

Available axle ratios

The 2019 Silverado 3500HD offered a range of axle ratios to suit various needs, from heavy-duty towing to more balanced performance. The specific ratio available often depended on the engine choice (6.0L Vortec gasoline or 6.6L Duramax diesel) and driveline (2WD or 4WD).

How to identify your axle ratio

For Chevrolet vehicles like the 2019 Silverado 3500HD, the easiest and most reliable way to identify your axle ratio is by checking the Service Parts Identification (RPO) sticker. This sticker is typically located on the glove box door, or sometimes on the driver's side door jamb. Look for three-digit RPO codes.

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

Alternatively, a GM dealership can provide this information using your VIN.

Towing vs MPG impact

Understanding the relationship between axle ratio, towing capacity, and fuel economy is crucial when configuring or purchasing a heavy-duty truck.

• Numerically Higher Ratios (e.g., 4.10:1): A numerically higher axle ratio means the engine will turn more revolutions for every rotation of the wheels. This provides greater mechanical advantage, translating to increased towing and hauling capability, better acceleration, and improved performance in demanding situations (such as steep grades). The downside is that at highway speeds, the engine will be revving higher, resulting in poorer fuel economy.

• Numerically Lower Ratios (e.g., 3.73:1): Conversely, a numerically lower axle ratio means the engine turns fewer times for each wheel rotation. This reduces the mechanical advantage, which can slightly decrease maximum towing capacity compared to a truck with a higher ratio. However, the engine will operate at lower RPMs at cruising speeds, leading to better fuel economy and a quieter ride on the highway.

For the 2019 Silverado 3500HD, the 3.73:1 ratio offers a good balance for most users who tow regularly but also value reasonable fuel economy. The 4.10:1 ratio is designed for those who consistently tow at or near the truck's maximum capacity or frequently haul extremely heavy loads, where maximizing pulling power is the top priority.

Common issues

While the drivetrains of the Silverado 3500HD are built to be robust, heavy-duty use can sometimes lead to specific issues:

• Ring & Pinion Whine: A common symptom of worn or improperly set up differential gears. This often manifests as a high-pitched whine that changes with vehicle speed and acceleration/deceleration. It can be caused by improper backlash, worn bearings, or damaged gear teeth.

• Carrier Bearing Wear: The bearings that support the differential carrier can wear out, leading to humming or growling noises, especially when accelerating or turning. If left unaddressed, this can lead to more serious differential damage.

• Limited-Slip Clutch Wear: Many Silverado 3500HD models are equipped with a limited-slip differential (LSD). Over time, the clutch packs within the LSD can wear out. Symptoms include a chattering or grinding noise from the rear end, especially when making turns at low speeds. This can often be resolved by replacing the clutch packs and ensuring the correct friction modifier is used in the differential fluid.

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