This service bulletin provides a comprehensive guide to performing an internal leakage test on TAS85 steering gears equipped with an internal pressure relief valve (PRV) sb4648. It covers a range of Freightliner truck models, including the FLA COE, FLB COE, FLD Conventional, Business Class, FLC 112 Conventional, Century Class Conventional, Argosy COE, Cargo, Columbia, Coronado, Business Class M2, and Cascadia. The manual delves into the detailed process of testing for internal leaks within the steering gear, providing step-by-step instructions and essential information to ensure accurate diagnosis and repair.

## Internal Leakage Test for TAS85 Steering Gears Equipped With an Internal PRV sb4648: Ensuring Optimal Steering Performance in Freightliner Trucks This internal leakage test is specifically designed for Freightliner trucks equipped with the TAS85 steering gear, a robust and reliable system commonly found in various models spanning from the classic FLC 112 Conventional to the modern Cascadia. The test focuses on the internal pressure relief valve (PRV) designated as sb4648, a crucial component responsible for regulating pressure within the steering gear. This valve plays a vital role in preventing excessive pressure buildup, ensuring smooth and predictable steering operation. By accurately identifying any internal leaks within the PRV, this test allows technicians to address potential issues before they escalate into safety hazards or costly repairs. The test itself involves a systematic process where the steering gear is pressurized and monitored for any signs of leakage. This process is crucial for maintaining the integrity of the steering system and ensuring optimal performance. Identifying and addressing internal leaks early can prevent a range of issues, including steering wheel looseness, erratic steering response, and potential failure of the steering gear. The test is applicable across diverse Freightliner truck models like the FLB COE, FLD Conventional, Business Class, Century Class Conventional, Argosy COE, Cargo, Columbia, Coronado, Business Class M2, and Cascadia, highlighting its broad applicability across various configurations and applications.