<p>Vehicle-to-Everything (V2X) communication technology plays a critical role for the safety and efficiency of intelligent transportation systems. With the increase of the number of sensors mounted on a vehicle and the data they generate, conventional sub-6 GHz technologies fail to meet the high data demands. Millimeter Wave (mmWave) technology with gigabit data rates is a promising solution. In order to address the high beam alignment overheads and high sensitivity to blockages of mmWave, and provide high-speed, low-latency and reliable communication, in this paper, we propose a sub-6 GHz V2X technology assisted mmWave Vehicle-to-Vehicle (V2V) communication framework. The framework consists of four phases, i.e., vehicle registration, mmWave link scheduling, beam training, and data transmission. By utilizing the four-phase design, the control and data planes are decoupled. The control plane estimates mmWave link blockages, maximizes the network utility in terms of vehicular adhoc network (VANET) data importance and freshness, and reduces mmWave beam alignment overheads to facilitate efficient mmWave link transmission of the data plane. In addition, uncertainties in vehicle information are considered to attain fine beam alignment. Three metrics are then proposed to measure the system performance, i.e., the ratio of successfully transmitted mmWave links, the network utility, and the average data transmission rate. Comparative simulation studies verify the effectiveness of our proposed sub-6 GHz V2X technology assisted mmWave V2V communication framework.</p>