Abstract: Gear shift movements from a main frame are transmitted to a gear transmission shift control, located on a sub-frame pivotally connected to the main frame, by means of a linkage system fixed at one end to the main frame and articulating at its opposite end with the sub-frame about an axis non-coincident with the pivot axis of the frames. The linkage system includes interconnected links, one of which being axially collapsible for transmitting rotational movement regardless of any sub-frame pivoting. The linkage system also includes a resilient cable which spans the collapsible link for transmitting axial movements thereacross.