Moving to the front of the transmission, Nusser pulls out the input shaft. "The stock input shaft is good to about 450 hp (flywheel)," comments Nusser. One of the biggest problems is not putting the shaft back in properly. As he points to here, there are wear marks on the shaft, and that is what should be slid back into the transmission. The metal becomes used to turning in one direction; when you change that direction, the shaft snaps even if you have just a few mods.