A vehicle traction control system for a vehicle, in which the vehicle has a prime mover, at least one wheel for providing tractive effort on a support surface, and a transmission having an input side operably coupled to the prime mover and an output side operably coupled to the at least one wheel, and in which the transmission has a controllable clutch pressure between the input side and the output side, includes a controller operable to monitor wheel slip of the at least one wheel. When wheel slip is detected the controller is operable to control the clutch pressure for modulating an output torque of the transmission for reducing the wheel slip. The clutch pressure can be controlled as a function of clutch slip.