Second opinions on transmission problems

[Johnie]

I'm working on my '64 long step that has a 283 and a Muncie 3 speed with an r10 overdrive. I rebuilt the motor and trans winter before last, but the clutch was replaced 5 years ago so I didn't replace any of those parts except the pilot bushing.

Everything was sweet as cream for a couple of thousand miles, but then it went sour. Sitting at a light with a slight hill, light turns green, I let out the clutch and BANG! It felt like I had been rear ended. Not a shudder, but a single sudden bang. It happens with the clutch all the way out, not as it is let out.

Grabbing the seat with my sphincter I ease iher back to the house, and it didn't give me any more trouble. I drove it a couple of thousand miles since, and the problem is random, but got worse and more frequent. I noticed the bell housing was wet with gear oil. So tonight I pulled the transmission expecting to see a dripping wet clutch disk. What I found was dry on the engine side, and a waxy scum on the transmission side.

Here are the questions:
1. I've never had a clutch slip like that. Is that how a greasy clutch slips?
2. I think the 4 bolts that hold the front bearing carrier were the cause of the leak. I didn't put anything on them and the holes go through. Carrier has a new gasket and the slinger is also new. The return drain was lined up and clear. Possible over filled too. Any other possible causes?