Products become more complex as the general technology development reaches new levels. These new technologies enable manufacturing companies to offer better products with new functionalities to their customers. Complex products require adequate manufacturing systems to cope with changing product requirements. In general, manufacturing of this type of products entails complex structured and rigid IT systems. Due to the system’s complexity and comprehensive structure, it becomes challenging to optimize the information flow. There are improvement potentials in how such systems could be better structured to meet the demands in complex manufacturing situations. This is particularly true for the vehicle manufacturing industry where growth in many cases have occurred through acquisitions, resulting in increased levels of legacy IT systems. Additionally, this industry is characterized by high levels of product variety which contribute to the complexity of the manufacturing processes. In manual assembly of these products, operations are dependent on high quality assembly work instructions to cope with the complex assembly situations. This paper presents a current state analysis of data and information handling in assembly information systems at multiple production sites at a case company manufacturing heavy vehicles. On basis of a certain set of characterizing manual assembly tasks for truck, engine and transmission assembly, this work focuses on identifying what data and information that is made available to operators in terms of assembly work instructions and the importance of such data and information. This work aims to identify gaps in the information flow between manufacturing engineering and shop floor operations. © 2017 The Authors