To execute a shift by using an electric coil assembly and a ball lump mechanism, in a gear transmission.

In a gear transmission having a main shaft 18 and a subshaft arranged in parallel in a housing 8, main shaft gears 22, 24 always meshed with a subshaft gear fixed to the subshaft are rotatably supported onto the main shaft 18. Jaw clutches 21, 23 supported to the main shaft 18 are moved in an axial direction, to be selectively connected to the main shaft gears 22, 24, so as to connect the main shaft gear 22 or 24 to the main shaft 18, a shift of the transmission is executed. A current is carried in coil assemblies 32, 33 clutch plates 52, 53 are friction connected to the main shaft gears 22, 24 control rings 37, 39 connected to the clutch plates 52, 53 and an operating ring 43 connected to the main shaft 18 are relatively rotated. By this relative rotation, ball lump mechanism 30, 31 are actuated to extend in an axial direction, the jaw clutches 21, 23 are connected to the main shaft gears 22, 24.