904 Shift selector & kick down lever

Can anyone tell me what the purpose of the spring is on the slide style kickdown/pressure lever currently on my car is for? I noticed that the 1 piece downrod examples shown in post 7 are secured to the short shaft. I have the sliding style and can't get the pressure correct however I could use the lockable and adjustable block like on this rusty pos I have pictured. Why the spring?




edit
here is the factory diagram