Overprocessing in the internal logistics of an automotive assembly plant occurs in the part sorting process identified at two sorting levels: The first level involves forklift drivers sorting parts at the skid level. In contrast, the second level entailed operators manually sorting box parts by assembly line addresses which supply by electronic car drivers via limited electronic cars and fixed routes that are unstable workloads and are inoperative under cycle time. This paper provided an approach to redesign internal routes with the Google Operation Research Tools (OR-Tools) to optimize route grouping for a balanced workload under cycle time. The simulation technique is applied to evaluate the performance of electronic car loaded capacity utilization and working under cycle time. The consequence of the calculation is the new route supply, which requires two modifications, i.e., to assign suppliers to allocate the parts boxes on the skid at a ratio of 1 skid per 1 new route to eliminate the manual box sorting process and to design the layout in transfer areas by new route for using the Automatic Guided Vehicle (AGV) system that instead of box parts sorting worker with lean manufacturing principles. The work finally concludes with a summary and outlook for the future.