I was driving my 84 and suddenly when shifting to 3rd there was no more drive. I was just coasting along and heard a few crunching sounds. When it rolled to a stop I tried all the gears and there was no drive and a few crunches and grinds, but mostly silence. The clutch action felt normal. I pushed it home and as it was rolling there were a few crunching sounds. Got it in the driveway and started it again and no drive in any gear, but an occasional violent clunk as if the gears caught for a second. I shut if off. Went back later and it drove up and down the driveway just fine in all gears. WTF? I though pinion or ring gear failure, but now it works...anyone have any ideas?