What would cause a noise when you release the gas pedal?

A noise when releasing the gas pedal can be caused by several factors, including a worn or damaged drivetrain component, such as the transmission or differential, which may create clunking or grinding sounds. Additionally, a loose or damaged exhaust system can produce rattling noises when the engine's load changes. Lastly, issues with the engine mounts or suspension components may also lead to noise as the vehicle transitions from acceleration to deceleration. It's advisable to have a mechanic inspect the vehicle to determine the exact cause.