PURPOSE: To reduce the speed change operation power by cutting the torque transmission to a counter shaft and an idler shaft when neutral position is set, by installing a transmission gear mechanism between an input shaft, counter shaft and an idler shaft.

CONSTITUTION: A transmission gear mechanism is installed between an input shaft 10, counter shaft 20, and an idler shaft 40. When a transmission 1 is at a neutral position, only a gear 11 for the first speed and a gear 12 for the second speed an the input shaft 10 revolve, and a counter gear 21 far the first speed and a counter gear 22 far the second speed on the counter shaft 20 are revolved. Since the counter gear 21 for the first speed and the counter gear 22 for the second speed are not connected with the counter shaft 20, the counter shaft 20 does not revolve. Though the gear 15 of a synchronizing device 71 on the counter shaft 20 and a counter reverse gear 41 on an idler shaft 40 are meshed at all times, the torque of the input shaft 10 is not transmitted to the idler shaft 40, since the counter shaft 20 does not revolve.