{"id":25208,"date":"2026-10-05T11:40:14","date_gmt":"2026-10-05T11:40:14","guid":{"rendered":"https:\/\/www.obd2tool.com\/blog\/?p=25208"},"modified":"2026-10-05T11:43:31","modified_gmt":"2026-10-05T11:43:31","slug":"john-deere-3518ct-s-torque-booster-maintenance","status":"publish","type":"post","link":"https:\/\/www.obd2tool.com\/blog\/john-deere-3518ct-s-torque-booster-maintenance\/","title":{"rendered":"John Deere 3518CT-S Combine Torque Booster Maintenance and Lubrication Guide"},"content":{"rendered":"

The torque booster in a John Deere 3518CT-S combine harvester plays an important role in the machine\u2019s continuously variable drive system. Proper Lubrication of the movable sheave, springs, cam mechanism, needle bearing, and bronze bushing is essential to maintain smooth speed adjustment and prevent expensive belt-drive failures.<\/span><\/p>\n

This guide explains how the torque booster works, where Lubrication is required, what happens when Lubrication is neglected, and what technicians should inspect when the combine develops CVT or drive-related problems.<\/span><\/p>\n

Important:<\/span><\/strong> Always confirm lubrication type, grease quantity, service intervals, and adjustment specifications against the service information for the exact machine serial number.<\/span><\/p>\n

How the Torque Booster Works<\/span><\/h2>\n

\"John<\/p>\n

The torque booster changes the effective pulley diameter of the belt drive to adjust travel speed and transmit torque under changing loads.<\/span><\/p>\n

During Speed Increase<\/span><\/h3>\n

When hydraulic pressure extends the speed-control cylinder:<\/span><\/p>\n

    \n
  1. The movable sheave of the intermediate drive assembly moves toward the fixed sheave.<\/span><\/li>\n
  2. The effective pulley radius increases.<\/span><\/li>\n
  3. Belt pressure against the torque booster increases.<\/span><\/li>\n
  4. The belt force compresses the springs inside the torque booster.<\/span><\/li>\n
  5. The torque booster\u2019s movable sheave moves outward.<\/span><\/li>\n
  6. Its effective working radius decreases.<\/span><\/li>\n<\/ol>\n

    The resulting pulley-ratio change increases rotational speed.<\/span><\/p>\n

    During Speed Reduction<\/span><\/h3>\n

    When hydraulic oil retracts from the cylinder, the process reverses.<\/span><\/p>\n

    The torque booster springs move the movable sheave toward the fixed sheave, increasing its effective radius. At the same time, belt force pushes the movable sheave of the intermediate drive assembly inward, reducing its effective radius.<\/span><\/p>\n

    The result is a lower drive speed.<\/span><\/p>\n

    How the Torque Booster Responds to Heavy Load<\/span><\/h2>\n

    When travel resistance increases sharply, it requires additional torque.<\/span><\/p>\n

    If the belt begins to slip against the torque booster\u2019s fixed sheave, the movable sheave and cam can rotate slightly relative to the fixed portion of the assembly.<\/span><\/p>\n

    This cam action pushes the movable sheave toward the fixed sheave and increases belt clamping force.<\/span><\/p>\n

    As belt grip increases:<\/span><\/p>\n

    Higher travel resistance \u2192 belt slip begins \u2192 cam mechanism reacts \u2192 pulley clamping force increases \u2192 belt slip decreases \u2192 more torque is transferred<\/span><\/strong>.<\/span><\/p>\n

    The intermediate drive assembly may also shift slightly as the drive ratio changes.<\/span><\/p>\n

    This mechanical response allows the belt-drive system to increase available torque when the combine encounters heavier operating conditions.<\/span><\/p>\n

    Critical Torque Booster Lubrication Points<\/span><\/h2>\n

    \"Torque<\/p>\n

    Correct Lubrication is one of the most important preventive-maintenance procedures for this assembly.<\/span><\/p>\n

    1. Torque Booster Springs<\/span><\/h3>\n

    The surfaces of the two springs inside the movable sheave hub should remain adequately lubricated.<\/span><\/p>\n

    Grease is supplied through the designated grease fitting.<\/span><\/p>\n

    The purpose is not only to reduce friction. The grease also helps protect the springs against moisture and corrosion.<\/span><\/p>\n

    Rust on the spring surfaces can eventually cause:<\/span><\/p>\n