Use with engines producing up to 750 foot pounds of torque in vehicles weighing up to 4000 pounds. Mainshaft is manufactured from proprietary steel billet material. Undercuts behind the splines are reduced, resulting in increased spline length and diameter, increasing spline engagement at the forward clutch hub and rear internal gear interfaces. Fully machined, shaped, and ground on precision CNC equipment. Fits 1997 and up models.