Final answer:
The crankshaft transfers torque to the transmission flywheel, which helps to smooth out engine vibrations by acting as a momentum storage device.
Step-by-step explanation:
The engine part that transfers torque to the transmission flywheel is the crankshaft. The flywheel, attached to the crankshaft, helps to smooth out engine vibrations caused by the thrust of individual piston firings.
This is because the flywheel acts as a momentum storage device; it stores energy when the engine power stroke generates more torque than needed for the current load, and releases it when the demand is greater than the power stroke can immediately supply, effectively averaging out the energy produced over each cycle of the engine's operation.