GEARS 101Updated 2 months ago

Standard vs. Reverse Rotation Gears

Let’s start with standard rotation versus reverse rotation ring and pinion gears. Despite the name, reverse rotation doesn’t mean the vehicle drives backward—it refers to the direction of the gear tooth cut and the way the pinion contacts the ring gear.

• Standard Rotation gears are typically found in rear axles and some front axles. These were the original design and have the pinion gear entering below the centerline of the ring gear.
  • Pros: Traditional, proven, and widely available.
  • Cons: When used in front axles, the pinion is lower and more exposed, and the tooth engagement under load isn’t optimal.
• Reverse Rotation gears are found in high-pinion front axles. These are engineered specifically for front axle applications where ground clearance, strength, and driveline angles matter.
  • Pros: The pinion gear enters above the ring gear centerline, offering better ground clearance and improved driveshaft angles. More importantly, the gears drive on the drive side of the tooth—the stronger side—when moving forward. This results in a stronger and more efficient gear mesh under forward load.
  • Cons: Not interchangeable with standard rotation—requires a specific housing and gear design.

We use reverse rotation gear sets in our ProRock 44™, ProRock 60™, and XD60™ front axles, because they're built with high-pinion geometry for front axle optimization. Meanwhile, standard rotation gear sets are typically used in our rear axles, such as the ProRock 60® rear or ProRock 80™ rear, where the low-pinion design is ideal for strength and efficiency.

Thick Cut Ring Gears

Another important gear setup we support is the thick cut ring gear. These are used to adapt higher (numerically lower) carrier break ratios without changing the differential carrier itself.

Here’s how it works:

• A traditional axle has carrier breaks—this means there are two different carriers for different gear ranges (e.g., 3.73 and down, 3.92 and up).
• Let’s say you have a carrier designed for 3.73 and want to run 4.56 gears. A thick cut gear allows you to do this without swapping the carrier. The gear face is thicker to compensate for the pinion position difference, keeping everything in proper mesh.

At Dynatrac, we design many of our axle assemblies to accommodate thick gears when needed, especially for customers upgrading to deeper gear ratios but wanting to retain their existing lockers or carriers. This is commonly seen in builds where a 3.73 carrier is reused with 4.56 or 5.13 gearsets.

Gear Type by Dynatrac Axle Model

Here’s how it all plays out across our product line: