Abstract: A drive chain assembly for vehicles having two chains, an idler sprocket, and a thrust link or strut. The first chain extending from the vehicle motor to the idler sprocket. The second chain extending from the idler sprocket to a driven axle sprocket. The second chain extending downwardly at a substantial angle from the driven axle to the idler sprocket and the idler sprocket supported on a mounting member which pivots on the same axis as the driven axle itself. The thrust link is pivotally attached at one end to the chassis of the vehicle near the engine and at its other end to the mounting of the idler sprocket. This strut forms one of the long side of a parallelogram linkage. The first short side of the parallelogram linkage is the distance between the pivot point at the engine end on the chassis for the strut and the engine sprocket. The second long side of the parallelogram is the first drive chain itself.