Farmall 300 clutch problem

I have a 1954 Farmall 300 row crop tractor with a TA and live PTO. I just rebuilt the tractor. When I say rebuilt I mean every piece was disassembled, cleaned, repaired, painted and reassembled with all new, high quality parts when needed. A rebuilt TA was installed. The flywheel was ground, new clutch disk, throwout bearing and a rebuilt pressure plate. The pressure plate has nine springs like the 400, not the same as an H. Everything was adjusted to factory specs. The tractor performed like a brand new machine for about six months of light to moderate use. I did some grading work which required a lot of shifting and some hard pulling but nothing abuseive. I used the TA under heavy loads and for less speed as needed. Everything was fine. I would push the clutch pedal all the way in, the transmission would stop, it shifted easy. When letting the clutch pedal out the TA clutch would engage first then the engine clutch would engage. It worked perfectly. One day doing some snow plough work I noticed the transmission would turn with the clutch pedal pushed all the way in causing it to be hard to go in gear. It wanted to grind. It got worse through the day. When the pedal was let out even a quarter inch the engine clutch would engage. As the pedal was let out more the TA clutch would engage. With the clutch pedal out the tractor operated as it should with no slipping and the TA would work in high and low. Now from a stop when the clutch is in, the transmission wants to turn so much the only way to get in gear is by grinding it in. The engine clutch is barely disengaging when the pedal is all the way down. The tractor takes off as soon as any pedal is let out. The pedal linkage, including the TA, on the outside of the tractor is adjusted correctly. I did take the cover under the engine clutch off today and did not see anything obviously wrong. The clutch plate is recessed in the flywheel so it can not be seen. When the clutch pedal is pushed in, at the end of the free travel, the throwout bearing is touching the three levers on the pressure plate. push a little more and the pressure plate starts to retract away from the flywheel. At this point the clutch should release but it dose not. I adjusted all of the free travel out of the pedal which did make it easier to shift. What could have caused this problem to spring up so quickly and what would the fix be? Incidentally the tractor had the same problem three years ago before I started the rebuild. At that time the clutch was at least 40 years old and the tractor was in rough shape.

Assuming you had the Flywheel cut to the correct step depth. Both the friction face, and the PP mounting surface must be machined), it sounds to me like the free play is not correct.
If the puin is out of the TA clutch, the pedal should move a little more than an inch when pushing it down by hand before the hand pressure builds from releasing the disk. If there is lost motion in the linkage, ot the "rebuilt" pressure plate has failed, the correct freeplay will not work. A warped disk will cause drag, A disk with decomposing friction material will also cause the issue if the material begins to stack up.
If the linkage motion is corect, I suspect the Pressure plate. Jim

I have checked everything and the problem is not the linkage, cross shaft, throwout bearing or pressure plate. I wonder if the splines in the new clutch plate have finally nested back into the old wear marks in the shaft? The shaft did not look that bad being a 60 years old. Everything else on the inside looked fine as I had recently taken it all apart. This is the exact problem that prompted me to rebuild the tractor in the first place. Well at least now it is clean and easy to work on.

Unless the wear marks were extremely bad, I don't see how that could be your problem. I would have expected the problem to have happened all at once, and soon after the rebuild.

I suspect either you got a bad clutch disk, or you bent the clutch disk putting the tractor together, and now it's coming apart. If you don't use the clutch alignment tool it's almost guaranteed that you'll be misaligned, and stabbing the tractor back together will bend the clutch disk.

The clutch pedal has a square headed stop bolt with a lock nut just below where the linkage from the front attaches to the pedal itself. Assuming the free travel has been set at 1 in from the deck plate, and the T/A lever linkage has been adjusted to give the correct free travel, per the manual, it sounds as if the new clutch has " worked itself in", I would back the stop bolt off a turn at a time until the tranny doesn't grind when going into gear. The clutch has "worn in" since you have really been working the tractor, that's all. If adjusting the stop bolt doesn't fix the grinding into gear, then the advice given above would be a good place to start.
The only other issue I can think of is on my 55 F300, the T/A "stops" the tranny when pushing the clutch pedal all the way down when stopped, about 1/2 to 3/4 in from the bottom the clutch is released from the engine and the T/A is just beginning to catch on the way out ? Hopefullly... someone more experienced here can explain it better, but I could never get the free travel, clutch pedal, T/A lever adjustment synchronized until I purchased a manual, once I adjusted everything in sequence to the manual & to the specs given, no more shifting problems.