Electric vehicles are projected to replace Internal Combustion Engine (ICE) vehicles in the next few years. Research related to electric cars continues to be carried out by experts. One of the essential parts of an electric vehicle is the powertrain, an electric motor. A car with ICE can be converted into an electric car by replacing the ICE with an electric motor. This research is strategic because it is forecasted that there are still ICE vehicles in the transition era of electric cars. If they are not converted, there will be many carcasses of the conventional vehicle. The authors converted an ICE vehicle into an electric vehicle. The car has a manual transmission system. The clutch system and existing transmission were still in use. This vehicle uses front wheels drive. The narrow space and the propeller shafts/front axles distance to the center of the transmission axis are also a challenge. So that the electric motor does not hit the propeller shaft, the electric motor was offset not in the exact center as the transmission axis. The use of an intermediate gearbox succeeded in overcoming these problems. It is actually a different fixed transmission, the ratio of which can be changed at any time. In order for the motor to be attached to the transmission, an intermediate flange was developed. It keeps the clutch functioning correctly. The system consists of an electric motor, a mounting flange, and an intermediate transmission. The housing material of those parts is aluminum. The housing manufacturing process was carried out with a CNC machine. Confidence in the strength of the motor design and material is vital. Strength analysis was carried out using the finite element analysis (FEA) method. Mainly, it is to see the value of strength, deflection, and safety factors. The design of the powertrain system worked well. © 2024 Author(s).