One of the weakest points of this transmission is the stock input shaft. At increased power levels, towing weight or in performance applications, the stock input shaft can break or twist. When this occurs, the transmission will lose movement and can damage the converter, pump and transmission. ATS recommends using a billet input with increased power and/or towing capacity/frequency. The theory behind a billet shaft is to increase the strength of the material and flex to absorb torsional loads. This allows it to reliably hold increase power levels. The ATS two piece billet input shaft is designed to increase the reliability of the transmission, withstand greater than stock power and torque converter lock-up in sooner-than-factory settings. While billet shafts are not indestructible, billet 300M material, coupled with stringent design and testing make them far superior to stock input shafts.