Which of the following is not a type of retarder? Question Which of the following is not a type of retarder? Answers Exhaust Engine Air Explanation Retarders are mechanisms in some vehicles that help slow the vehicle and reduce the need for braking. The four basic types of retarders are exhaust, engine, hydraulic, and electric. This questions appears in the following tests: Alaska Class A Knowledge Test Mississippi Class B Knowledge Test Missouri Class B Knowledge Test Nebraska Double Nevada Double Wyoming Double