2001-2016 Billet Input Shaft Allison 1000 And 2000 Series (128020000)Description The transmission input shaft is tasked with transferring the horsepower from the torque converter to the transmission. Due to its placement,the part needs to be tough because it is subjected to a huge amount of twisting torque. The PPE Billet Input Shaft has been specially designed to withstand higher horsepower and torque levels (over 800 RWHP) that come with high performance engines or the added stress that comes with towing or racing.