Quality in the automotive industry means development and manufacturing of vehicles whose specifications meet customer requirements. Among many other quality issues, door closing effort is a vehicle characteristic that strongly affects the customer first opinion about vehicle design. The door closing effort is affected by uncertainties in materials and manufacturing processes. The present paper presents a reliability-based method to evaluate the uncertainties associated with door closing effort due to manufacturing processes. A formulation is proposed to calculate that energy based on three components: energy used to compress air into the vehicle, energy used to compress the sealing and energy used to lock the door. In order to quantify the probability that the door closing effort is greater than a target value, reliability analysis concepts are used based on the uncertainties associated to latch position.The Monte Carlo simulation is used to define door closing effort variability due to variation of the side door latch position. That analysis allows defining maximum allowable latch and striker position variability in order to keep door closing effort below a target value. The latch position uncertainty is modeled by a probability distribution defined based on data collected from the assembly process. The probability of having a door closing effort magnitude lower than a target value is then calculated. Simulated distribution is compared to experimentally door effort analysis showing very good agreement between them. The simulation based model is used to evaluate the feasibility of manufacturing processes changes to reduce door closing effort.