Abstract: A tow truck of the type having wheels supporting it for movement along a path defined by a subfloor conveyor. There is a vertically movable tow pin at the front of the truck for vertical movement in and out of driving engagement with the conveyor. An accumulation bumper at the front of the truck is movable between a forward normal running position and a rearwardly retracted accumulating position when the bumper engages an object ahead of the truck. A connecting mechanism between the bumper and tow pin includes at least one bell crank member pivoted for rotation on a transverse axis behind the tow pin with a first lever arm projecting upwardly and connected by a link to the bumper, together with a second lever arm projecting forwardly and connected to a vertical lift rod, the upper end of which is operatively connected to the upper portion of the tow pin.