mine has a 17 but I was also wondering about the tranny
Well, if you can rent one or borrow one first, you can test it out.  My JD (and probably yours) has a "pin" between the axle and the drive wheels.  The pin shears before the tranny does.  It looks like a square piece of metal.   Sometimes they are known as shear pins or shear keys.
So, if you care to test it, you shouldn't lose the transmission. 

=J