A control system/control method for controlling the jaw clutch engagement and at least partially automated multiple speed change gear mechanical transmission (10) is provided. The control includes a central processing unit (106) for receiving signals indicative of transmission input shaft (16) speed, transmission output shaft (90) speed and of a selected ratio to be engaged. The control unit initiates/permits engagement of the jaw clutch members associated with the selected ratio upon sensing that the rotational speed of the input shaft falls within a calculated synchronous window. The control unit senses vehicle start from stop conditions and/or degraded clutch operation during vehicle start from stop conditions and responds thereto by enlarging the synchronous window.