Fading CV Joint clunk?
 

I have a repeating clunk/noise that comes from the left rear of my 75 911S when I first drive it. After driving for a short while the noise lessens to the point where it's bearly audible. From researching previous threads, it's sounds (no pun intended) like I have a bad CV joint. Right? Would the sound fade like mine if I had a bad joint? If yes, could it just need greasing?

I would look at the CV Boots (all four) to determine if there is a break in the rubber. Start simple then work out.

I'm wondering if that is the CV Joints. Are you certain it is from the left rear? Can you properly supprt your vehicle as outlined in 101 Projects (A book we should all own and buy from the host) where the left rear wheel is able to spin freely. While in Neutral, try spinning the wheel at slow speeds and gradually increase the speed. See if you can hear the noise. switch wheels and compare. You might hear the noise coming from the bearing or from the CV Joint. You should be able to rule out these places or isolate to the problem quickly.

Hope some others pipe in, please keep in mind that I am no expert though I've offered to play one on a TV show (they turned me down, laughing)