2018 Volvo VNL Transmission & Axle Gear Ratios

The 2018 Volvo VNL is a powerhouse of the North American commercial trucking industry, heavily praised for its driver comfort and powertrain integration. At the heart of its performance is the seamless communication between the engine, transmission, and rear axles. Whether you are running long-haul interstate routes optimizing every drop of diesel, or pulling heavy loads through mountainous terrain, the specific gear ratios in your VNL dictate its performance profile.

Below is a comprehensive guide to the transmission internal gear ratios and rear axle ratios available on the 2018 Volvo VNL.

Transmission gear ratios

For the 2018 model year, the undisputed star of the Volvo VNL powertrain is the Volvo I-Shift 12-speed automated manual transmission. While Eaton Fuller manual options (10, 13, or 18-speed) could be spec'd for specific vocational or heavy-haul needs, the vast majority of VNLs feature either the Direct Drive (AT2612F) or Overdrive (ATO2612F) I-Shift variants.

Volvo I-Shift 12-Speed Direct Drive (AT2612F)

The direct-drive transmission features a 1.00:1 ratio in its top gear. This configuration is incredibly popular in Volvo's XE (eXceptional Efficiency) packages, pairing a direct drive top gear with a fast (numerically lower) rear axle ratio to minimize parasitic drivetrain losses.

Volvo I-Shift 12-Speed Overdrive (ATO2612F)

For fleets prioritizing flexibility across varying terrain, or for those pulling heavier gross weights, the overdrive variant offers a deeper gear reduction in lower gears and a 0.78:1 overdrive top gear.

Available axle ratios

The 2018 Volvo VNL uses axles from both Volvo's proprietary lineup and outside suppliers like Meritor. Your axle ratio must be perfectly matched to your transmission type (direct vs. overdrive) and your tire size to achieve the engine's "sweet spot" at highway cruising speeds.

How to identify your axle ratio

Identifying the exact axle ratio on a Class 8 truck like the 2018 Volvo VNL is straightforward if you know where to look.

1. Door-jamb RPO sticker / Specification plate: Open the driver-side door and look at the primary manufacturer data plate (often located on the door itself or the B-pillar jamb). This sticker contains the truck's Gross Vehicle Weight Rating (GVWR) and often explicitly lists the front and rear axle capacities along with the rear axle ratio.
2. Axle tag: Crawl under the rear of the tractor (ensure the truck is safely parked, chocked, and the suspension is supported) and locate the metal identification tag bolted to the rear differential carrier housing. If you have Meritor or Dana axles, this tag will boldly stamp the gear ratio (e.g., "RATIO 2.64").
3. VIN decoder: Because commercial trucks are heavily customized at the time of order, running your truck's 17-digit Vehicle Identification Number (VIN) through a commercial truck VIN decoder or calling a Volvo Trucks dealership parts department is the most foolproof method.

Towing vs MPG impact

The relationship between your transmission's top gear and your rear axle ratio dictates engine RPMs at highway speeds.

• Numerically lower ratios (e.g., 2.47, 2.64): These are known as "fast" gears and are heavily utilized in Volvo's XE downspeeding packages. They allow the engine to cruise at lower RPMs (often between 1,050 and 1,150 RPM) at 65 MPH, vastly improving fuel economy. However, they sacrifice low-end startability and are not ideal for heavy, vocational towing.
• Numerically higher ratios (e.g., 3.36, 3.55): These are "slow" gears. They provide greater torque multiplication, resulting in better startability on steep grades and vastly improved towing characteristics for heavy haulers. The downside is reduced fuel economy due to higher engine RPMs at highway speeds.

Common issues

While the 2018 Volvo VNL powertrain is highly reliable, high mileage and immense torque loads can eventually lead to driveline wear:

• I-Shift Actuator and Air Leaks: The I-Shift relies on pneumatics. Air leaks or a failing clutch actuator can cause the transmission to miss gears, shift harshly, or drop into neutral.
• Ring & Pinion Whine: If you hear a howling or whining noise from the rear of the cab under acceleration or deceleration, it may indicate excessive wear or improper backlash in the ring and pinion gears.
• Power Divider / Inter-Axle Differential Wear: Drivers who forget to disengage the inter-axle differential lock when returning to dry, high-traction pavement can cause catastrophic wear to the power divider, leading to metal shavings in the fluid and total failure.
• Carrier Bearing Failure: Vibrations felt through the floor at specific speeds often point to a worn driveshaft carrier bearing or worn U-joints, which should be inspected immediately to prevent further driveline damage.

Find a driveline shop on Repairius to keep your Volvo VNL running smoothly, securely, and efficiently for the long haul.