A flexplate or flex plate is a metal disk that connects the output from an

engine An engine or motor is a machine designed to convert one or more forms of energy into mechanical energy. Available energy sources include potential energy (e.g. energy of the Earth's gravitational field as exploited in hydroelectric power ge ...

to the input of a

torque converter A torque converter is a device, usually implemented as a type of fluid coupling, that transfers rotating power from a prime mover, like an internal combustion engine, to a rotating driven load. In a vehicle with an automatic transmission, the ...

in a car equipped with an

automatic transmission An automatic transmission (AT) or automatic gearbox is a multi-speed transmission (mechanics), transmission used in motor vehicles that does not require any input from the driver to change forward gears under normal driving conditions. The 1904 ...

. It takes the place of the

flywheel A flywheel is a mechanical device that uses the conservation of angular momentum to store rotational energy, a form of kinetic energy proportional to the product of its moment of inertia and the square of its rotational speed. In particular, a ...

found in a conventional

manual transmission A manual transmission (MT), also known as manual gearbox, standard transmission (in Canadian English, Canada, British English, the United Kingdom and American English, the United States), or stick shift (in the United States), is a multi-speed ...

setup.

Design

The name refers to the ability of the disk to flex along its main axis to account for gear changes and/or small misalignments as rotational speeds change. Flexplates are generally much thinner and lighter than flywheels not only because of the required flexibility, but also due to the smoother coupling action of the torque converter and the elimination of the

clutch A clutch is a mechanical device that allows an output shaft to be disconnected from a rotating input shaft. The clutch's input shaft is typically attached to a motor, while the clutch's output shaft is connected to the mechanism that does th ...

surface. Like a flywheel, a flexplate normally handles coupling to the

starter motor A starter (also self-starter, cranking motor, or starter motor) is a device used to rotate (crank) an internal-combustion engine so as to initiate the engine's operation under its own power. Starters can be electric, pneumatic, or hydraulic. T ...

via

gear teeth A gear or gearwheel is a rotating machine part typically used to transmit rotational motion and/or torque by means of a series of teeth that engage with compatible teeth of another gear or other part. The teeth can be integral saliences or ...

cut along its outer edge. These teeth give the flexplate a gear-like appearance in spite of this being a secondary function. Flexplates come in many forms, but are usually either stamped steel (for road cars), a

machined Machining is a manufacturing process where a desired shape or part is created using the controlled removal of material, most often metal, from a larger piece of raw material by cutting. Machining is a form of subtractive manufacturing, which util ...

two-piece

billet In European militaries, a billet is a living-quarters to which a soldier is assigned to sleep. In American usage, it refers to a specific personnel position, assignment, or duty station to which a soldier can be assigned. Historically, a billet w ...

(for race cars), or a machined one-piece billet (for high-performance drag racers).

References

Automobile transmissions {{automotive-tech-stub

Design

See also

References