Control system for limiting engine speed down on automatic transmission

Abstract

With respect to an automatic transmission in a motor vehicle, which transmission has a vehicle speed-sensitive governor valve and a throttle valve responsive to the intake manifold vacuum, the control system comprises a solenoid-operated selector valve which causes the vacuum chamber of the throttle valve to communicate with either the intake manifold or the atmosphere and a temperature-sensitive switch which is attached to the engine for energizing the selector valve, so that the vacuum chamber is allowed to communicate exclusively with the atmosphere when the engine temperature is not high enough to allow after-burning of the exhaust gas in a thermal reactor attached to the engine, resulting in occurrence of a shifting at a higher engine speed.