Input Shaft
The shaft in a transmission that receives power from the engine clutch or torque converter.
The input shaft (also known as the clutch shaft) is the rotating metal rod extending from the front of the transmission housing. Its primary function is to receive rotational power from the engine and transfer it to the internal gear sets of the transmission. On manual transmissions, the input shaft is splined and carries the clutch disc; on automatic transmissions, it connects to the turbine inside the torque converter.
The nose of the input shaft typically rides inside a pilot bearing or bushing in the center of the engine crankshaft, which keeps it aligned and prevents radial runout. The shaft passes through a front seal (input shaft seal) that prevents transmission fluid or gear oil from leaking into the bellhousing.
Because it must transfer the engine's full torque, the input shaft is made of high-strength forged steel. Excessive engine torque, severe clutch drops, or a failed pilot bearing can bend the input shaft or strip its splines, leading to severe transmission vibration, gear noise, and clutch damage.