Flexplate
A lightweight, flexible metal disc that connects the engine's crankshaft to the automatic transmission's torque converter, featuring a ring gear for the starter.
A flexplate is the automatic transmission counterpart to a manual transmission's flywheel. It is a thin, circular steel plate bolted to the rear of the crankshaft. The torque converter of the automatic transmission is bolted directly to the flexplate.
Because automatic transmissions generate hydraulic pressures that can cause axial movement, the flexplate is designed to flex slightly front-to-back to absorb these forces and prevent damage to the engine bearings. Around the outer edge of the flexplate is a ring gear that meshes with the starter motor pinion to crank the engine.
Flexplates can crack or warp over time, leading to clicking or rattling noises at idle, starter engagement problems, or drivetrain vibrations. Replacing a cracked flexplate is a major repair requiring separation of the engine and transmission.