How to bleed the Hydro Gear Transaxle on a 25 HP Craftsman Lawn Tractor?

I have a problem with my sears tractor which is a 25 hp tractor about 15 years old. I was working in the edge of my woods when a branch laying on the ground hooked on one of the hoses on my hydrostatic drive. I took it back to my workshp and drained the fluid, cleaned the filter and replaced the hose and refilled the transaxle to as near as I could tell the amount that came out. This is a Hydro Gear Transaxle, Mod. #218-3010 which is the sears number. I have reverse but nothing in a forward motion. There has to be air in the system but I cannot figure out how to bleed it. The only thing the sears manual says that it is a factory sealed unit and has no need for any type of maintenance for the life of the transaxle. Any help would be greatly appreciated.
Thanks