2024 GMC Sierra 1500 Transmission & Axle Gear Ratios

Transmission gear ratios

The 2024 GMC Sierra 1500 offers a range of sophisticated transmissions designed to optimize performance, fuel efficiency, and towing capability. The specific transmission you have depends on your engine choice.

8-speed automatic (GM 8L90)

This transmission is typically paired with the 2.7L TurboMax engine.

10-speed automatic (GM 10L80)

This advanced transmission is standard with the 5.3L V8, 6.2L V8, and 3.0L Duramax Turbo-Diesel engines.

Available axle ratios

The axle ratio plays a crucial role in how your Sierra performs, affecting acceleration, towing capacity, and fuel economy. GMC offers several axle ratios for the 2024 Sierra 1500, varying by engine and trim level.

How to identify your axle ratio

The easiest way to determine the axle ratio of your 2024 GMC Sierra 1500 is by checking the RPO (Regular Production Option) sticker. This sticker is typically found on the inside of your glove box door or sometimes on the driver's side door jamb.

Look for a three-digit code starting with "GU."

• GU5: Indicates a 3.23 axle ratio.
• GU6: Indicates a 3.42 axle ratio.
• GT4: Indicates a 3.73 axle ratio.

If the RPO sticker is missing or unreadable, you can sometimes find an axle tag bolted to one of the differential cover bolts on the rear axle. This tag will have the ratio stamped on it.

Alternatively, a GMC dealership parts department can tell you your vehicle's original specifications using your VIN.

Towing vs MPG impact

The axle ratio has a direct and significant impact on your truck's performance characteristics:

• Numerically Lower Ratios (e.g., 3.23): These ratios mean the driveshaft spins fewer times for each rotation of the wheels. This results in lower engine RPMs at cruising speeds, leading to better fuel economy. However, it also means less torque multiplication to the wheels, reducing acceleration and towing capability.

• Numerically Higher Ratios (e.g., 3.73): In contrast, higher ratios cause the driveshaft to spin more times per wheel rotation. This provides greater torque multiplication, which is excellent for heavy towing, hauling, and off-road acceleration. The trade-off is higher engine RPMs at cruising speeds, resulting in decreased fuel economy.

• Balanced Ratios (e.g., 3.42): A mid-range ratio offers a good balance between fuel efficiency and towing capability, making it a popular choice for many owners who need versatility from their truck.

Common issues

While modern differentials are highly durable, certain issues can arise with prolonged use or improper maintenance.

• Ring and Pinion Whine: A common symptom of worn or improperly set up ring and pinion gears. This often manifests as a howling or whining noise that changes with vehicle speed and whether you're accelerating or decelerating. It can be caused by improper backlash, worn bearings, or damaged gear teeth.

• Carrier Bearing Wear: The carrier bearings support the differential carrier within the axle housing. Worn carrier bearings can lead to a rumbling or growling noise, especially when cornering or accelerating. If left unattended, this can cause further damage to the ring and pinion gears.

• Limited-Slip Differential Clutch Wear: If your Sierra is equipped with a limited-slip differential, the internal clutch packs can wear out over time. Symptoms include a chattering or clunking noise from the rear end when making low-speed turns, or a reduced effectiveness of the limited-slip feature.

Regular differential fluid changes with the correct specification fluid are crucial for longevity and preventing these issues.

Find a driveline shop on Repairius.