It used an new design of a 4WD transmission designed by Keith Duckworth . This transmission was different from the Ferguson transmission used by all other 4WD F1 cars of the 1960s . The car , designed by Robin Herd , used an original 4WD transmission designed by Keith Duckworth ( different from the Ferguson used by all other 4WD F1 cars of the 1960s ) and powered by a magnesium version of the DFV unit .