I bought a 1967 gas 580 CK with mechanical shuttle. I knew it had shift problems when I bought it but it would go into reverse. It sat for a few years and I've started to work on it now. It won't shift into reverse. The gears start to grind when moving the lever. It will shift into forward. I pulled the shuttle cover off and it does have a broken blocking ring which seems to be the obvious reason, and I do have a new one. I can't figure out why it would shift when I first brought it home but won't now. My question is do you think the broken brass/bronze blocking ring is the only problem? I can't figure out why it grinds if I have the clutch depressed. Nothing should be spinning in the gear cases with the clutch in correct? I thought the clutch may need adjustment, but it works in forward. Any help appreciated.
That broken thing is a synchronizer. It essential in transmissions to prevent gear grinding and allow shifting while in motion. You need to repair it as soon possible. Your gears don't look to happy either.