1975 and earlier hydro static transmissions for brands like Ariens, Allis, Homelite, Gilson, and Simplicity were Vickers T66 models like the ones below. After 1975 those brands switched to Sunstrand hydro static transmissions. Bolens used Eaton and later switched to Sunstrand, while Cub Cadet was Sunstrand all along. The cast iron Vickers Hydros were nearly 50 pounds heavier than the Sunstrand models.