Sugar Beet Harvesters belong to self-propelled agricultural machinery for trimming, lifting, cleaning and collecting sugar beets. Like most harvesting machines such vehicles are equipped with hydrostatic traction drives to ensure a continuously variable speed adjustment to the harvesting process. These drives are state of the art, but rather moderate in efficiency. For further enhancement of efficiency the hydrostatic system was replaced by a diesel-electric traction drive. The two different systems were tested and compared in simulation and field tests. The result was improved driving performance at reduced fuel consumption.