That could mean the stub shaft is broken at the MM gearbox tail, or it could mean that the driveshaft from the stub shaft to the mower is broken. (more likely). These drive shafts are plentiful, often on eBay for example. There are different lengths, though as some of the JD front mowers use a very similar shaft. The length differences can be an inch or so (in my case). I have a MMM shaft and its very similar to the F935 front mower, snow blower, and leaf blower driveshaft. But, they are not the same. Some are interchangable. The ones that are too short will pull apart if the mower deck goes down into a ditch. Then it will break apart: been overtraveled. Note that the connectors at each end are the same: a spline on the transmission end and a keyed/ offset thru bolt on the other.
Meanwhile, on the tailshaft, that part comes off a gear in the front of the transmission. It ought to be easy to fix. The whole assembly plops out after removing a few bolts. Recall that its an option, so it should be easy to replace.
