A control system in a vehicle in which at least one pair of driving power transmission members are engaged with each other with a slack on a driving power transmission path, comprises an input shaft rotational speed detector for detecting a rotational speed of an input shaft located upstream of engaged portions of the driving power transmission members in a direction in which the driving power is transmitted, a determiner for determining whether or not the driving power transmission members are in a non-contact state at the engaged portions for a period of time based on a change rate of the detected input shaft rotational speed, and a controller for controlling the vehicle to reduce a rotational speed difference between the input shaft and an output shaft located downstream of the engaged portions, when the determiner determines that the driving power transmission members are in the non-contact state.