93 124 rear end knock / clunk

[Scooter76]

Howdy folks. 1993 300E, 2.8 - For the last couple weeks, I've noticed a pronounced "clunk" coming from the rear end when I go from reverse to drive while backing out of the driveway - it'll only do it if my foot is off the brake when I make the shift. Now yesterday I noticed that I'm getting a rythmic clunking from the same area when accelerating from a stop - only though about 5-10 mph under torque, then it disappears. If I accelerate very gently, it won't do it. Could be my imagination, but it seems worse if I happen to be making a turn while doing this. I didn't have time to get it up in the air last night, but I did look the CV joints over briefly and didn't notice any torn boots. If it is indeed a CV joint, I'll be relieved, but I'm very scared that maybe it's the diff because I noticed the rear end is wet with lube (although not dripping anything on my driveway).

Also, why is it that most of the parts houses only list/carry the "inner" CV joint - is that the more common one to fail? If it is a joint, am I better off getting an entire axle assembly or just the joint? New price is $900 and some change for the half-shaft - I think I've seen a few rebuilt units for around $300. Any thoughts on the issue would be most appreciated.