Can a tranny knock like an engine on start-up?

[kelsfine69]

87 Silverado 350/700R4. Every morning when I go to work something is knocking like an engine rod knock. Thats exactly what it sounds like and then after about 5 seconds its gone and doesn't return till next morning on first start-up. I thought ok drive it till it craters then drop in a new crate engine. But it wont die. 2 years and counting. If it was a rod bearing it would of packed it in long ago? I'm now starting to think its the tranny?. Its really hard to hear where its coming from, but its loud. I have a vibration as well that has always been there since I bought it. I believe its the torque converter so Im thinking about getting the tranny rebuilt and see if thats it. They did have problems with vibrations due to torque converters back in the 80's..