Thought I would share this.
JD 650. Going from gear to gear was fine, but after starting in neutral I was grinding just to get it into gear. Time to replace the clutch.
Splitting the tractor was not hard at all. Luckily for me instead of removing the engine with the front end, I opted for removing the front end and then taking the engine out with a crane.
Used a cold chisel to start the separation, but the most I could get between the engine and bell housing was about a half inch. No amount of jerking, pulling, or prying (and I used a 6 foot piece of pipe as a lever at one point) could get much more than another 1/4 inch. It was stuck fast. Damn!
After thinking about it for a while, I went to Runnings and got a large sample of M10 Bolts with the longest thread (x1.75 I think) they had, some M10 threaded rod and M10 nuts. The plan was to use them as a makeshift "press" to force the engine off while keeping everything aligned.
I started by rotating the engine a few degrees so the mounting holes didn't line up any more and then threading 3 of the long bolts through from the engine side so they could push against the transmission housing (they would normally be inserted from the bell housing side). I wanted to use 4, but the left side of the engine has no holes near the top that are accessible to thread a bolt in from the front. If I got desperate, I was going to remove one of the starter mounting studs and use that threaded hole.
Taking care to screw them in evenly a bit at a time and whacking the top left of the engine with a hammer occasionally to keep that portion in line, I reached the limit of the bolts (they were threaded all the way in). At this point I was going to resort to the threaded rod with a nut between the engine and transmission to do the pushing, but as I tightened the last bolt to its limit there was a satisfying loud "pop" and the engine was free.
When I unbolted the pressure plate, the friction material with it's backing plate fell out. Just the outer part of the clutch plate. The center portion of the clutch plate was cupped and wedged into the pressure plate so tight I could not budge it with a hammer. What had apparently happened was that the clutch plate had seized onto the first motion shaft preventing me from extracting the engine and probably explaining why the gears were grinding going from neutral with the clutch engaged to clutch disengaged and shifting to any gear.