Patent ID: 8234945

Claim:
A transmission in which a first clutch is provided between an internal combustion engine and one end part of a first main shaft, a second clutch is provided between the internal combustion engine and one end part of a second main shaft running coaxially and relatively rotatably through the first main shaft, and gear trains of multiple shift stages are provided between the first main shaft and a countershaft and between the second main shaft and the countershaft so that the gear trains can be alternatively established, wherein: a plurality of odd number stage gear trains are provided between the second main shaft and the countershaft and arranged so that a first speed gear train is disposed on the opposite side to the first and second clutches, an end part of the second main shaft on the opposite side to the first and second clutches is rotatably supported on an engine main body via a main shaft side ball bearing having a larger diameter than an outer diameter of a first speed drive gear provided integrally with the second main shaft so as to form part of the first speed gear train, and an outer race of the main shaft side ball bearing is fixed to the engine main body via a fixing plate engaging with an outer peripheral part of the outer race, an end part of the countershaft on the opposite side to the first and second clutches is rotatably supported on the engine main body via a countershaft side ball bearing, and an outer race of the countershaft side ball bearing is also fixed to the engine main body via said fixing plate, and the fixing plate is configured and dimensioned to cover less than half of the circumference of each of the respective outer races, and is fixed to the engine main body by a bolt which is disposed further from an axis of the countershaft than an outer diameter part of a first speed driven gear which is mounted on the countershaft, an annular recess is provided on the outer race of the countershaft side ball bearing, the fixing plate engages with the annular recess, and the fixing plate has two arcuate ends formed therein to conform to the respective shapes of the ball bearing races engaged thereby.