I know most think it is a hydrostatic but it is not. It more like the ATV belt drive system that uses two sliding sheave pulleys and a single speed manual transmission. The system principal is sound but it just the design of this one just not well thought out for mower service as mowers are rather dirty with clippings and other debris finding its way on to transaxle. Once you get a look at it you will see just how flimsy it is designed. They have come with a debris shield for it but I have only see of these in my shop and the customer is definitely not happy with it.
Nath also not all pedal speed controlled mowers are hydros as MTD uses a belt drive version with their sliding sheave pulley setup and their single speed transaxle but a lot of my customers thinks they are hydrostatics. Now MTD does have hydrostatic setup on some their newer mowers using the Hydro Gear hydrostatic transaxle.
On a side note I have heard that manufactures are considering put a belt system similar to the ATV system into automobile service.
