The ATS Billet output shaft is part of the back bone of your transmission. It is the first hard part to bring power into the transmission and transmit that power to the wheels. With no dampening or power loss other than the torque converter, the shafts in your transmission have a lot to handle. Now add power, weight from a trailer, bigger tires (and is some cases all these things together) and you will be well beyond what that factory shaft was designed for.
The theory behind billet shafts is not quite what you may have in mind. The key to success is not to make the shaft stronger necessarily, but give it the ability to absorb more torsional load. The way we do this, is by using billet shafts, they have the ability to rotate further with out breaking. This is going to give the transmission more give and allow it to transmit more torque and more load with out breaking.
Along those lines, breaking a shaft can lead to costly repairs Details: