Service Kits (POSI) Preload Kit

The Detroit Locker-TracTech Service Kits (POSI) Preload Kit (Part Number 29590-00S) is a precision differential spring and plate assembly designed to establish correct preload settings in limited-slip and locking differentials. This kit addresses a critical maintenance requirement: ensuring proper spring tension between differential carrier components. Correct preload prevents unwanted noise, excessive wear, and inconsistent lock-up behavior that can develop over thousands of miles of operation.

The preload assembly is engineered to work across multiple differential sizes—8.2, 8.5, and 8.875 inches—making it compatible with a broad range of truck and performance vehicle applications where Detroit Locker differentials are factory equipped or retrofitted. Proper preload is fundamental to differential longevity: insufficient preload allows excessive play between gears and can result in catastrophic wear; excessive preload generates drag and heat. This kit contains the springs and plates required to set preload within manufacturer specifications, restoring performance after bearing wear or during full differential rebuild. The compact 0.89 lb package contains all necessary components for a complete preload setup.

This preload kit is essential for differential technicians, serious off-road enthusiasts performing their own maintenance, and builders restoring high-mileage or damaged limited-slip systems. Whether diagnosing differential noise, completing a full rebuild, or replacing worn preload components, this Detroit Locker-TracTech service kit provides OEM-equivalent components at the foundation of reliable differential operation. Proper preload setup is not optional—it directly determines whether a rebuilt or serviced differential will perform smoothly and survive years of load cycles.