Your transmission has a service advisory concerning leaking axle seals. part number 753-08294A is the seal repair kit for your transmission. It comes with both axle seals, a new sealing cover on top where you add the oil, and new bolts that hold the wheels on the axle.
I also noticed a goof in the parts diagram. It shows the hydrostat tranny under the drive section, a separate section just for the parts diagram of the tuff torq tranny, but at the bottom of the list shows a section for transmission which looks like shouldn't be there since it is the normal gear drive single forward/reverse MTD transmission which isn't used on this mower.