Abstract: Synchronous wheel slip control is desirable in a locomotive having wheels driven by at least one traction motor which receives power from an engine driven generator. Wheel slip control in known systems involves increased cost and complexity resulting from sensors required to determine an actual locomotive speed. In the subject invention a microprocessor under software control is used to detect and control synchronous wheel slip. Generator current and voltage are measured and used in an empirical relationship to calculate an actual locomotive speed. A first-order-lag of the actual locomotive speed is calculated and compared to the calculated locomotive speed. If the compared values differ by more than a preselected reference a synchronous slip condition exists and the generator power is reduced by a preselected magnitude. The generator power is incrementally reduced until the synchronous slip condition is no longer detected.