Detroit Truetrac - Ford 9in 31-Spline

The Detroit Truetrac differential carrier for Ford 9-inch differentials is a helical-gear limited-slip unit designed to deliver controlled traction across a wide range of driving conditions. Built for 31-spline axles with a 3.25 ratio and up, this steel carrier balances torque distribution between wheels while maintaining smooth on-power and off-power transitions. The Truetrac design makes it an ideal retrofit for street vehicles, weekend warriors, and off-road applications where improved traction without the engagement harshness of a locker is preferred.

The helical gear geometry of this differential carrier provides automatic torque biasing, sending more power to the wheel with better traction while allowing the inside wheel to slip during cornering. Unlike open differentials, which split torque equally regardless of traction, the Truetrac actively responds to wheel speed and load differences. The 31-spline design confirms compatibility with modern Ford 9-inch housings and axles rated for higher horsepower applications. At 16.82 lbs, the carrier integrates directly into factory 9-inch cores, preserving OEM housing geometry while upgrading differential performance.

This is the correct choice for builders seeking improved traction during acceleration or cornering without the mechanical noise and engagement feel of a spool or locking differential. Street machines, muscle cars, hot rods, and off-road vehicles all benefit from the Truetrac's seamless power delivery. The 3.25-ratio specification supports both performance and highway cruising in most applications; verify your existing ratio before ordering to ensure compatibility. Installation requires removing the original differential carrier and installing the Truetrac unit into your existing Ford 9-inch housing.