A History of the HY-Driv SystemBy far the majority of Colt/Case/Ingersoll garden tractors made for the past 40 or so years have had the patented HY-Driv system, which is a hydraulic drive system that powers a mechanical, two speed transaxle. This system, developed by Colt in 1962 was originally called a HYDRA-static drive, which caused a lot of confusion with owners who thus assumed they had a hydro-stat. Case shortened the name to Hy-Driv in the late 60's.
The Case 117 (1972) and the 118 (1973-76) had true hydrostatic transmissions but no hydraulic take off - the mower and snow blower were belt driven off of the front of the engine. The 100 series tractors were on a smaller, light frame, not nearly as heavy duty as the 200 or 400 series tractors. The drive wheels on the 100 series were 8 inches, compared to the 12 inch tires on the 200 series and 16 inch tires on the 400 series.
The 316 & 318 LGT (2001-04) are also true hydrostats made on the 3000 series frame that has a belt driven mower deck and a mechanical lift. This is the size tractor that replaced the 200 series, and has 12 inch drive wheels. It has no provision for running hydraulic powered attachments.
So if you really want a hydrostatic drive Case or Ingersoll garden tractor, it would be one of these 4. They didn't make one that could run hydraulic powered attachments.