2014 Kenworth W900 Transmission & Axle Gear Ratios

The 2014 Kenworth W900 is an iconic Class 8 heavy-duty truck known for its classic styling, immense capability, and high level of customizability. Because it is utilized in everything from long-haul highway freight to severe-duty logging and heavy hauling, the W900 could be spec'd with a massive variety of powertrains. At the heart of this customization is the driveline, featuring industry-leading transmissions from Eaton Fuller and axles from Dana Spicer and Meritor.

Understanding your gear ratios is critical whether you are spec'ing a truck for a new route, diagnosing drivability complaints, or trying to optimize your fuel economy.

Transmission gear ratios

The 2014 Kenworth W900 was primarily equipped with Eaton Fuller manual and automated manual transmissions, ranging from 10-speeds for standard freight to 18-speeds for heavy hauling. Below are the internal gear ratios for two of the most popular heavy-duty transmissions found in the W900: the Eaton Fuller 18-speed (RTLO-18918B) and the 13-speed (RTLO-16913A).

Eaton Fuller 18-Speed Manual (RTLO-18918B)

Eaton Fuller 13-Speed Manual (RTLO-16913A)

Available axle ratios

Kenworth W900s utilize tandem drive axles typically supplied by Dana Spicer or Meritor. The optimal ratio depends entirely on the truck’s application—highway cruising versus severe vocational use.

How to identify your axle ratio

Identifying the exact axle ratio on your 2014 Kenworth W900 is relatively straightforward. Heavy-duty truck manufacturers provide several clear identification methods:

1. Door-Jamb Data Plate: Open the driver’s side door and locate the vehicle identification tag (often referred to as the data plate or line sheet sticker). This plate lists the truck's VIN, Gross Vehicle Weight Rating (GVWR), engine specs, transmission model, and the front and rear axle models alongside their exact gear ratios.
2. Axle Tag: If the door tag is missing or unreadable, crawl under the rear of the truck. Dana and Meritor both affix a stamped metal identification tag directly to the differential housing (usually attached via one of the carrier mounting bolts). This tag will indicate the axle model (e.g., DSP41) and the ratio (e.g., 3.55).
3. Kenworth Dealer / VIN Decoder: You can provide your 17-digit Vehicle Identification Number (VIN) to any local Kenworth dealership. Their service department can pull the original factory build sheet, which details every driveline component installed on the assembly line.

Towing vs MPG impact

In the Class 8 trucking world, selecting the correct axle ratio is a delicate balancing act that directly impacts your bottom line.

Numerically lower ratios (e.g., 3.25, 3.36) are "taller" gears. They allow the engine to spin at lower RPMs at highway speeds (e.g., 65-70 mph), yielding better fuel economy (MPG). However, they provide less torque multiplication for getting heavily loaded trailers moving from a dead stop.

Numerically higher ratios (e.g., 3.90, 4.10, 4.30) are "shorter" gears. They offer maximum torque multiplication, which translates to better startability on steep grades, off-road conditions, or when pulling oversize/overweight loads (better towing). The trade-off is higher engine RPMs at highway cruising speeds, which burns more fuel and increases cabin noise.

Common issues

While the driveline components on a W900 are built for extreme durability, they are not immune to wear and tear, especially given the massive torque outputs of modern diesel engines.

• Power Divider (Inter-Axle Differential) Failure: A common operator error is leaving the inter-axle lock engaged on dry pavement, which causes driveline wind-up and eventually shears the power divider components.
• Ring & Pinion Whine: Heavy hauling, particularly up steep grades, generates massive heat. If the gear oil is not changed at proper intervals, it degrades, leading to scoring on the ring and pinion gears. This usually manifests as a noticeable whine that changes pitch depending on whether you are accelerating or coasting.
• Carrier Bearing Wear: The sheer length of a W900 wheelbase means it has a long, multi-piece driveshaft. Center support (carrier) bearings frequently wear out from the vibration and torque, causing a shuddering feeling under heavy acceleration.

If you're dealing with a howling differential or need your Eaton Fuller transmission rebuilt, don't leave it to chance. Find a driveline shop on Repairius.