How does hydrostatic drive work?

stllbrake1 this could be as simple as not having enough oil in the drive or even old oil. Now to get a better idea of what is going on, we would need your exact model mower. I believe that Craftsman uses Hydro Gear transaxles. Most of those take 20W50 motor oil. There should be a plug at the top of the transaxle where you can check the level, number 109 in the diagram is the typical location for those transaxels.

"If it’s simply low on drive oil, you’re in luck.

If yours also has a little age on it, it’s possible you need to change the fluid out. Some say it’s better to go to a higher weight gear oil, if you change it out.

Also, it’s possible that it’s just wearing out, too, in which case you’d need to replace the trans-axle."