Traction Upgrades

Open Differentials

Most vehicles come with an Open Differential from the factory. This type of differential does a great job of smoothly transmitting power to the rear wheels, while also allowing for the rear wheels to turn at different speeds. This was an important development in automotive design because when a vehicle is cornering, the wheel on the outside of the corner turns faster that the wheel on the inside of the turn. (the outside wheel travels further). Without this ability, the rear tires will chirp and squeal when cornering and excessive tire and drivetrain wear will occur. The rear wheels will also cause the vehicle to understeer or push through corners.

While the open differential is perfectly fine in dry pavement or high traction scenarios, they perform poorly in low traction situations. For example, if one tire is on ice and the other is on dry pavement, the tire on the ice will spin and little or no torque will be transferred to the wheel with traction. This also occurs on uneven surfaces that flex the vehicles suspension and attempt to lift a tire off the ground.

The Traction Devices described below are designed to provide traction to both wheels at the same time when needed. The differential experts at Ring & Pinion Service can recommend and install the best unit to fit your performance and budget needs.

Limited-Slip / Positraction Differentials

Limited-Slip or Positraction (Posi) type differentials come as a factory option in some vehicles, usually pickup trucks. This type of differential still allows for some difference in speed from one side to the other while cornering, but are designed to mechanically bind depending on the difference in wheel speed. Typically, as one wheel starts to spin, more torque will be applied to the non-spinning wheel resulting in continued forward motion. Some of the factory limited-slip differentials are prone to failure, necessitating replacement with a more durable model. There are numerous limited-slip differential designs, including the clutch-type and helical gear styles that we recommend. One of our favorites is the Truetrac, a helical-gear style positraction from Eaton Performance featuring no clutches to wear out. We also carry clutch-style limited-slips including Auburn Gear’s HP, Pro and Race Series, as well as the Eaton Posi from Eaton Performance Differentials.

Automatic Locking Differentials

Locking differentials are designed to provide 100% traction to both wheels when needed, regardless of traction conditions. Automatic type lockers require no driver input and allow the wheels to rotate at different speeds while cornering, albeit with some ratcheting or jerking while cornering. The automatic locking differentials we carry include the Detroit Locker from Eaton Performance and the Lockright, a budget locker that replaces the internals in an open differential.

Selectable Locking Differentials

Selectable Locking Differentials offer the best of both worlds. When disengaged, this type of locker performs like an open differential allowing for perfectly smooth and quiet cornering. By activating a switch in the driver’s compartment, the differential can be switched to a fully locked mode providing 100% traction to both sides regardless of traction conditions. The Selectable Locking Differentials we carry at Ring & Pinion Service include the air-actuated ARB Air Locker, The electronically actuated ELocker from Eaton Performance and the ECTED Max Locker from Auburn Gear. Most ECTED models operate as a limited-slip until actuated, and then lock completely.


A spool is designed for racing applications and does not allow for ANY difference in wheel speed. 100% traction is applied to both wheels at all times. On a street driven vehicle, the result is tires barking when cornering and excessive tire wear. Off road the spool will attempt to push the vehicle forward in a straight line and will tend to inhibit cornering. RPS carries two different types of spool, both of which achieve the same performance result. The Mini Spool fits within the existing carrier assembly and eliminates the spider gears. A Full Spool replaces the entire carrier assembly.
To discuss your Gear Ratio, Axle Upgrade and Traction needs with one of our Differential Experts, call us at (916)635-9665. We can help you determine the ideal upgrades to fit your style and budget.