Abstract: An apparatus for mounting an aerodynamic device, preferably the top center portion of a three-piece wind deflector, to the roof of a truck cab wherein the mounting apparatus includes a base member attached to the cab roof, a forward link pivotally connected to both the device and the forward portion of the base member and a rearward link, preferably of selectively variable length, pivotally connected to the rearward portion of the device and to the base member. The forward and rearward links form, with the base member and device, a four-bar linkage, disposed to shift the forward edge of the device still more forwardly relative to the cab roof as it moves from a raised position to a lower position and thus maintains the rearward edge of the device more nearly over the cab roof in the lowered position. A locking plate is preferably provided to secure the forward link to the base member in either the lowered or raised position and may be slotted to control the movement of the forward link.