The only reason for the slot and spring is for safety. Watch the linkage work. When you open the throttle, the pin is at the back of the slot, and pushes the linkage rearward, as soon as the throttle moves. When the throttle is released the spring keeps the linkage against the pin. There is actually no difference in the operation, then if there was a hole in the link rather the a slot. The problem with having a hole, instead of a slot, is if something jams the trans linkage, so it cannot return. It would then hold the throttle open, and the car would not slow down. With the slot and a relatively weak spring, even if the trans linkage should jam wide open the throttle would still close, and you could safely stop the car.

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Charrlie_S
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