From Moss Motoring 1984
If your transmission acts like the clutch is not fully disengaging, (grinding while shifting, etc.), the problem may be the clutch or pressure plate, your hydraulics (The slave cylinder rod should move about an inch or so.), or lastly, the Notorious Throwout Fork Pin, Moss part #596-040. Every TR2 thru TR6 has this pin, which often shears and causes the release fork to rock on the shaft even though the pin is tight. This also means that moving the slave cylinder rod will not push the release fork until the rod is towards the end of its travel. Solution: Pull the trans, and replace the pin, making sure to wire it in so it doesn’t unscrew. If you are unable to extract the broken part after it shears, you’ve got a problem which can be solved easily: With the fork facing out, drill a small hole into the release fork over where the pin is secured, and then punch out the pin. Be sure to always check the pin whenever you have your transmission out.