The input (turbine) shaft transmits the power from the torque converter to the transmission. Increased power levels and heavy loads can exceed the OEM shaft and hub capacity. Torsional overloading can result in shaft fraction or stripped splines in clutch hub. Severe damage to the pump or torque converter may occur. To address this Sun Coast recommends our 300M alloy steel shaft and 4140 hub. There is no additional labor charge for this option when purchasing the Sun Coast transmission assembly.