The bell crank they are referring to is the collection of levers on top of your tramsmission that take the camle movement and transfer it into the correct movement for the transmission. (They are gold /brass colored) The term bellcrank can be used to reger to anything that uses leverage to cause motion though a linkage. For instance, the thing your throttle cable attches to on the throttle body is called a bellcrank. The term originated from the use on leverage and a cam on an axle to cause motion in large bells in churches, goverment buildings, etc. The cam the rope was attached to was called (of course) a bell crank.