In this paper we investigate the application of time constant to estimate the convective heat transfer coefficients from experimental vehicle-level test data. For simulation of vehicle components temperatures, heat transfer coefficients are critical pieces of information that must be known with a reasonably high level of accuracy. Available data from literature are based on empirical equations that may or may not apply for the components of interest. The variation in accuracy depends on the geometry of the components being investigated and the airflow around it. In this approach, the vehicle speed is allowed to run in a step change under fixed engine load and ambient temperature. The test is allowed to continue until component temperature reaches steady state. The time constant for each component is determined from the response curve. From the time constant data, convective heat transfer coefficient can be determined. This process is applied at various speeds so the heat transfer coefficient can be determined as function of vehicle speed.