I have a 25 hp -50 Filling transaxle with fluid?

Check transaxle bypass is closed (rod is all the way forward).

Remove c/v shaft after you get the axle nut off pry drive shaft out of trans axle . ( I assume this is where the leak is) use a small part bar to pry out old seal. Tap into the transaxle the new seal with a small hammer . go slow be careful not to bend the seal. Lube inner lip of seal with vasaline or grease reinstall CV shaft . check fluid level in transaxle . use a repair Manuel to locate the place you have to fill the transaxle and fluid type

My first thought is to make sure the unit is full of fluid in the drive.

There is a plug about halfway up in the transaxle, fill till lube runs out. You will need a new seal in the unit eventually, but if leakage is not real bad you can just add the oil recommended by the manufacturer. Hope this helps, plese post solved on fixya.com. So I get credit for a solved problem if it does. If not, check back and give me more info.

This can be a loose belt that is slipping, low fluid in the transaxle, a bad pump (if hydrostatic transaxle) or worn gears, start by checking belt tension, then replace the fluid and filling to proper level, if that fails, the trans will need to be inspected for internal damage to pump and gears

The hydro Transmisson Is not the easyest to repair. That is probably way they said that. plus the labor whould have been $350 to $500. So most shop won't repair them.
Find A break down on line so you can see what your getting into.

The filter is not replaced unless an overhaul of the trans-axle is needed, It involves the removal of the trans-axle and partial disassembly to accomplish the filter replacement. That is only if trans failure is suspected, and diagnosis requires removal and inspection of the filter. The filter removal and replacement is procedure 42 out of 72 in the disassembly manual and 12 different Ford specific SST's (Special Service Tools) are needed. I did however, include the procedure for the normal drain and fill service performed at the dealer.
I hope this info helps!
subyguru
Transmission Fluid Drain and Refill

Specifications

Material

Draining

1. With the vehicle in NEUTRAL position it on a hoist.

1. NOTE: If an internal problem is suspected, drain the fluid through a paper filter. A small amount of metal or friction particles may be found from normal wear. If an excessive amount of metal or friction material is present the transaxle will need to be overhauled.

Remove the transaxle drain plug.

Refill

1. Using a small amount of pipe sealant on the threads, install the transaxle drain plug.

• Tighten to 27 Nm (20 ft. lbs.) .

1. Fill the transaxle with clean automatic transmission fluid.
2. Start the engine and run through all the gears and check fluid level.

If it is going ok, i would leave it alone, you can drain and refill the hydro unit if you wish, there are two main manufacturers of the units, Hydro Gear, and Tuff Torque, the hydro gear gearbox takes a 20-50 oil, and the Tuff torque takes a 10-40 oil, neither takes a hydraulic oil, if you do decide to drain it, you will need to purge the unit of air after re filling, this will mean running the engine with the unit in by pass, make 5 slow forward engagments and 5 rear engagements, then take the unit out of by pass and do the same again, each time come back to neutral, do this as many times as it takes for any noises to dissappear and the machine moves smoothly, the biggest killer of the unit is over loading ( brakes binding, towing, cooling fan blocked with grass ).

Hydrostat transaxles are very picky like the trans in your car. It must have clean fluid and be full of fluid. I am not saying to fill that transaxle to the top but make sure it is to the top of the fill line. Also it needs to be changed every few years and keep it clean to help it stay cool. If it has a filter make sure to change it when you change the fluid in the transaxle. That fluid is nothing more than 20-50W motor oil.

It sounds like the oil in transaxle is degraded.The transaxle is supposed to be a sealed unit requiring no service but over time the oil will get dirty enough to cause problems like you are describing.Remove the back hitch plate and look at the transaxle it will have a rubber vent hose or a 1/4 alllen wrench fitting on top. You will need to purchase a battery suction bulb from sears automotive and use it to remove as much oil from transaxle as possible. Warm the transaxle up first by running it around,then suction the oil out.Refill with a good synthetic motor oil 15w-50 or 20w-50 like Amsoil or Mobil 1.Do not use transmission fluid or hydraulic fluid. When adding the new oil back fill it to within 1.5 in from the top,be sure to allow this amount of air space in top of transaxle for expansion.