In production systems, the assembly line is widely used to manufacture products that have a set of repetitive activities and well-defined sequences. The efficiency of the assembly lines impacts the entire manufacturing process, and the optimization of resources is essential in this context.  Balancing the distribution of activities to be performed by the workstations is still a challenge in the project, especially in the operation of mixed product assembly lines. The difficulty occurs due to the large variation between the times of the activities of the various types of products, and short-term changes in the sequencing of these products. The present work proposes a dynamic balancing system that considers the effects of product sequencing changes on resource utilization, and that is based on the determination of specific sets of sequenced activities for each product type and operator, implementing more flexibility in workstations. This system uses balancing strategies through the application of precedence diagram and heuristic algorithm of positional weights. The modeling and simulation of this system is performed using the Colored Petri Net. To illustrate the main characteristics of this approach, a case study is presented which has as research object a truck assembly line in operation in Brazil. The results show that it was possible to: reduce the dependency on product sequencing; meet cycle time requirements; reduce by 12.5% the resources with acceptable average occupancy; and define a system for use by assembly line managers.