Abstract: The transmission is intended to effect synchronism between the speed of an engine and the speed of a transmission input shaft. An engine drive clutch and gearbox combination is provided which comprises automatic change speed to engage and disengage the drive clutch and to select a required gearbox ratio. A further clutch is also provided which is responsive to said change speed to control engine speed during a ratio change with the drive clutch disengaged. The further clutch reacts against the output shaft of the gearbox to synchronize engine speed with the speed of the transmission input shaft during the ratio change and enables drive to be transmitted between the engine and output shaft with the drive clutch disengaged.