Disengage old hydrostatic transmission m11

You did not post model number so I guessed.

Brake is on trasaxle. Follow brake linkage and determine cause.

For complete manual;
https://manualsbrain.com/en/manuals/819931/#google_vignette

Moving Machine by Hand
CAUTION: When the bypass valve is open, the machine will
have unrestricted motion.
• Do not open the bypass valve when the machine is stopped
on an incline to prevent it from going downhill out of control.
IMPORTANT: Transmission damage may occur if the machine is
towed or moved incorrectly:
• Move machine by hand only.
• Do not use another vehicle to move machine.
• Do not tow machine.
1. Unlock the park brake.
2. Put automatic transmission shifter into center position.
GXAL41998—UN—04MAR13
3. On automatic and hydrostatic Models: Pull out on bypass rod (A).
4. Push machine to desired location.
IMPORTANT: Hydrostatic transmission might be damaged if the
bypass rod is not pushed back to operating position before
attempting to start the engine. Do not start or operate the
machine with the bypass rod in the pulled-out position.
5. Push bypass rod back in.
6. Lock the park brake.

If you have an air compressor set it about 2 lbs and try and blow fluid out. If you have a slurp gun you can suction fluid back thru fill hole.

If it is a hydrostatic transmission, they have a lever (on the rear of the mower) that will lock out the transmission to allow pushing / towing.

The drive belt may be broken, or it may have slipped off a pulley.

Is the hydrostatic drive disengaged? On some mowers there is a lever on the hydrostatic drive you can flip to disengage so the mower can be pushed or towed. Other possibility is a broken hydrostatic drive belt.

Under the seat there is a hole with a bent rod coming up through it. Grab the rod and lift, there will be a flange on the rod the you will need to navigate through the hole and lift above the chassis and lock into the notch. That will allow you to push or tow the mower.

This is when you put the shifter to NUETRAL, both shifter. The propeller may turn from where the 2 wheels on ground but it turns freely since the gears inside the transmission is disengaged.

If it is automatic the quick is a two wheeled tow dolly. Or if that is not desirable then a RV repair shop can recommend a towing package that will disengage the torque converter in the transmission. Either way is about 1K.

Craftsman-Husky...same tractors-built in the same factory. I also had a problem with the hydrostatic transmission not providing power to the rear wheels. Here's what Sears told me:
(1) Check to make sure the drive belt is tight both under the engine-and the tranny.
(2) Air can get into the hydrostatic transmissions-especially during shipping (new mower) and storage.
So.....
Pull your freewheel pin out to disengage the tranny-then push the mower both forward and then backwards for 50' or so. Then push the freewheel pin back in and start the mower. If the transmission then works-drive forward-then backward-then forward repeating the cycle about 4 times. Drive about 50' in each direction. This should purge the air from the treansmission.