Clunking from gearbox/transfer box at low speeds

My searches on the forum have n't help me flush out diagnosing an worsening issue I have with my 1995 110. The car has a R380 with LT230 transfer box, it has started clunking when I manoeuvre in first or second gear, it seems more pronounced when turning, the clunk sends a shock through the drive line that can be quite violent and felt through the gearstick, at first i thought it was popping out of gear but its not (but sounds like it), if i hold the clutch down and roll it helps and suppresses the noise but there is a courseness in the drive train as the vehicle rolls. I have jacked the car off the ground and turned the wheels, props etc, checked the A frame ball joint, even tested with it off the ground engine running in reverse/first to see if I can't replicate the noise. Any thoughts appreciated.

Given what you have already done try the following.
1. Jack front axle and with wheels at full lock spin by hand, may be CV problem.
2. Remove front prop and drive in diff lock and see if clunk goes away.
3. Same with the rear prop.
4. Drive in a straight line with diff lock in, [ both props on ] clunk goes quite may mean problem with centre diff

Thanks for the reply, I will start exploring what happens with props on off this weekend. it only clunks with the steering turned, it does it in low and high ratio. Today I reversed in a circle, also forward in first going in circle, changing directions. It would intermittently clunk three or four times then seem to stop allowing me to keep circling with no noise, same when changing direction. The interesting bit was that I slowed to a halt, whist the clutch was down and not moving it clunked with one of its big thuds!