Weird Vibration!

Actually I've rebuilt a bunch of these & my memory must be going too. You can't just remove the trans tail housing. To get at that release ring, you have to do more disassembly. The main gear set with syncros etc. comes out with the tailhousing, only then can you get at the release ring to pull the gearset off. You more or less have to disassemble most of the tranny. Not terribly difficult but this is what you have to do. What you really need is a service manual. Here's a pic of the bushing-
http://www.passionperformance.com/c44.html