JD 1 and 2 series tractor have had serious problems with the driveshaft Ujoints, the front one virtually impossible to service without removing a bunch of stuff. Mine on the 4010 (like a 2019E, if they made it) blew apart at 660 hours and 9 years. At that time, they did not have zerks on them, and JD did not recommend any service. Now, they've provided zerks on them and say to grease at 50 hours, but you cannot get to the front one. Cost me $470 to get them greased and PTO button replaced (another issue) at 200 hours ($120 of that was for them to get it and return it).
My 1025R (have a 2025R now, much like the 4010) in between was a real lemon. The only good things about it were the more comfortable seat and the gentle startup of the PTO.
Never used an underbelly mower to comment about that.
Ralph