Spec Clutch ST634 Stage 4 Carbon Puck Clutch Kit

The Spec Clutch ST634 Stage 4 Clutch Kit is a race-grade, solid-hub clutch system engineered for heavily modified engines demanding maximum torque transfer and near-instant engagement. As a solid-hub evolution of the Stage 3 kit, it eliminates the sprung hub in favor of a rigid 8-rivet solid hub assembly that is heat-treated for superior strength and durability under extreme competition conditions.

Available in 3, 4, or 6-puck configurations to suit your specific performance needs: the 3-puck disc delivers the lightest rotating mass for all-out performance, the 6-puck offers the smoothest engagement of the three options, and the 4-puck strikes a balance between the two. The kit pairs a high-clamp pressure plate with carbon-graphite friction material to achieve a torque capacity of 520 lb-ft, making it well-suited for high-output forced-induction and heavily built naturally aspirated applications.

Kit Includes:

• High-clamp performance pressure plate
• Carbon-graphite friction disc (3, 4, or 6-puck configuration)
• High-torque solid 8-rivet hub and disc assembly (heat-treated)
• Release bearing
• Installation tool kit

Specifications:

• Input Spline Quantity: 21
• Input Shaft Diameter: 1.125 in.
• Flywheel Included: No
• Torque Capacity: 520 lb-ft
• Disc Quantity: 1

Ideal Applications: Drag racing, road racing, drifting, rally, pulling, and circle track. Note: Due to the rigid solid hub design, this clutch is not intended for street use. Stages 1–3+ are recommended for street/strip driving; the Stage 4 is a race-only component.