General Hydraulic Auxiliary Drive (HAD) W55.90-1000-00 Overview of HAD system components 1 Front axle 2 Side module 3 Valve control block 4 High-pressure pump 5 Expansion reservoir 45 i Introduction of the New Truck Generation - The New Arocs (Model 964) – This printout will not be recorded by the update service. Status: 01 / 2013 –