In the disaster site, mechanisms which can run on uneven and soft ground, and narrow space is needed. In this paper, we study omnidirectional crawler and propose solution to the problem for the yawing-axis helical gear transmission we devised. The yawing-axis helical gear transmission is able to allow the deflection of the height direction because end of the crawler in transverse displacement unit is driven directly. We design to reduce imbalance of power on the rack gear and the gap between transverse displacement units. In addition, we confirm the basic principal of the mechanism and effect of solution through experiment.