The actual quotient of the engine speed and sensed speed of the driven wheels is compared to a reference quotient calculated from the engine speed and the instantaneous gear ratio. When wheel vibrations affect the sensed wheel speed signals to an unacceptable degree, the actual quotient will deviate from the reference quotient by more than a prescribed amount. A reference wheel speed calculated from the reference quotient and the engine speed will then be used to determine slippage values, which in turn are used to generate control signals from braking and limiting engine torque. The reference wheel speed may either be used to replace the sensed wheel speeds or to limit the increase in the sensed wheel speeds.