In a manual transmission, which shaft is connected to the engine when the clutch is engaged? Input shaft. The transmission’s input shaft receives rotational power from the engine through the engaged clutch.
The engine’s crankshaft turns the flywheel, which presses against the clutch disc when the clutch is engaged. The disc is splined to the transmission input shaft, so engine rotation is passed into the gearbox. In many longitudinal layouts, the input shaft then drives a countershaft whose permanently meshed gears provide the available ratios.
The output shaft is the shaft that ultimately sends torque onward toward the driven wheels, usually through a driveshaft and differential in a rear-wheel-drive car. It is therefore a common wrong choice: it carries power out of the transmission, but it is not the shaft directly connected to the engine through the clutch.
“Engaged” can also cause confusion. In normal automotive usage, the clutch is engaged when the pedal is released and the clutch disc is gripping the flywheel. Pressing the pedal disengages the clutch, separating engine rotation from the input shaft so the driver can change gears or stop without stalling.