While your'e going through it, just a couple suggestions. There is a grease fitting on the drive shaft, at the engine coupling. That coupling is a splined hub that is bolted to the crankshaft pulley, then the drive shaft slides over it. On the shaft yoke there is a fitting. Grease it. While under there check the u-joints. If they're loose, replace them before it takes out the entire shaft (which is about $500 or something like that)...or the transmission.
There's also a grease fitting hidden on the bottom of the front axle pivot. Hit that one too. That one lubricates both the axle pivot AND the PTO shaft bearings, at the same time.
Them are the two major issues, those and electrical. Rest of the mower seems to be pretty stout. I have my 1800 apart in the shop because of a failed rear u-joint. I caught it JUST in time. It was vibrating pretty bad and I grabbed the shaft to check the joints...it was loose as a goose and actually the shaft was hitting the floorboard. Just got it back in, now time to see if I can tighten up the front axle somehow...it's also loose. May need to shim it. I picked this thing up for my dad, the exterior is clean as a whistle but they forgot about those grease fittings.
There is also an electrical connector under the radiator. I forgot about it until I removed the engine to get the shaft out, so I'm going to clean that one up as well while it's easy to get to.
If you have to do the drive shaft, removal of the engine is by far the easiest way, IMO. Takes about an hour. MUCH easier than removing all of the steering pedestal stuff which is usually stuck, and if you do it that way the radiator still has to be loosened/moved in order to wiggle the shaft out. Engine off, pull shaft right out the front after removing the fan from the back of it. If the fan is damaged, replace it before the transmission gets overheated/destroyed like so many BX's I've had to do as of lately.
