Providing service parts is the biggest single drain on profits .
The cost of running a spare parts network is enormous and despite what most think , spare parts sales do not make a fortune for the manufactures, the only people who make a profit from them are the retailers.
Because of this where ever they can manufactures do not have any support for major components.
So the engine is a complete unit which no mower makers parts on it and same story for the transmission.
Thus all they have to supply is the complete transmission and not the 200 individual parts inside it.
So service information & parts will have to come directly from the transmission maker