Transmission Controlled Spark

Transmission controlled spark is designed to allow distributor vacuum advance in high gear only. System is made up of a solenoid control switch, an ambient temperature override switch (on pre 1973 1/2 models only), and a coolant temperature override switch. Transmission switch is mechanically operated by shifter shaft on manual transmission models, and by speedometer gear speed on most automatic transmissions. Solenoid control switch opens or closes to allow or disallow vacuum advance.