Yes, you must use the linkage and it is not really a 'kickdown' linkage, rather it is called a 'trottle valve' linkage. This is a necessary piece of information that any automatic tranny needs to do it's job properly. Info needed includes, 1) gear detent - input from the driver when he selects the gear he needs, 2) car speed - input from the governor on the tailshaft of the tranny, and 3) throttle position (load demand) - input by various means from the carburetor. Examples of the latter are TH350 uses a cable, TH400 uses an electrical switch, and the old 4-speed dual range hydramatic used a mechanical rod and lever. Some trannys also use a 4th piece of information - a vacuum modulator which reads intake manifold vacuum. The governor and thorttle valve, and sometimes vacuum modulator, are needed so the transmission will shift at the proper rpm and with the appropriate firmness for the conditions. Without them, the tranny would shift at exactly the same point and with exactly the same harshness or softness, regardless of speed or load. One additional feature of the throttle valve is that it will kick down the tranny to passing gear,if the governor tells it that it is ok to do so, thus the incorrect name people give it.
[ February 11, 2003: Message edited by: firstname.lastname@example.org ]</p>