TCS Switch, Pin Style Connection,  mounts on transmission. This connects to the transmission cover, and when you shift into 4th gear, it advances the timing of the distributor for better gas mileage and drive ability. This is the switch that mounts into the manual transmission covers on all Muncie M20 / M21 / M22 & Borg Warner T10 transmissions. This transmission spark control switch fits most all GM models with the above transmissions.