PURPOSE: To prevent gearing noise by temporarily shifting an immediately preceding gear to a synchronous gear position, when a gear in a transmission gear is shifted to a non-synchronous gear position, and confirming vehicle speed thereafter shifting to non-synchronous gear position.

CONSTITUTION: A vehicle speed sensor 17 is backed up by an output from a rotation sensor 30 coupled to the counter shaft of a transmission gear 7. When the vehicle speed sensor 17 malfunctions, a speed change control unit 13 is in backup mode. When the gear of the transmission 7 is shifted to non- synchronous gearing position because the gear has been shifted to neutral position for long time and the vehicle sensor 17 can not be backed up, the gear is shifted temporarily to synchronous gearing position through an actuator 11 so as to confirm the vehicle speed through the rotation sensor 30. Thereafter, the gear is shifted to desired non-synchronous gearing position. Consequently, the gear can be shifted automatically to an optimal gearing position without causing gearing noise even if the vehicle speed sensor 17 can not be backed up.