More info (for anyone still paying attention
). The soft thunk from the rear happens when I put the car in gear. So, car stopped, foot brake applied, clutch in, slide into 1st - clunk. Doesn't happen every time, but most times.
I'm really leaning towards a bad u-joint, which means a new drive shaft (& center bearing & probably giubo). I guess I might just have to drop the exhaust to check it. Sigh.