my to35 did that once.
got the tractor stuck plowing and mud plugged up the drain hole in the bottom of the trans housing.
after getting the tractor un-stuck i did not check to be sure the drain hole was open.
oil built up in the trans housing and the first thing i notice was oil coming out of the starter.
then i unplugged the drain, but by that time oil had gotten onto my clutch plate.
I had to have a new or rebuilt clutch/pressure plate installed.
all because i did not check that drain hole.
that drain hole is your friend, need to get in a habit of checking it each time you fuel tractor.
mine has an up side down cotter key in it that turns as you drive through grass and keeps the drain hole open.
hope you have not ruined your clutch.