sometimes it even make a sound like... 'grook!!'
whut do u mean by 'shot transmission'?
He means you might have a broken gearbox...to put it simply. It only happens with reverse? It could be your gearbox or it could just be that your shift stick is slightly mis-aligned. Could be a worn out mounting or bush. If all your other gears are working perfectly normal then I don't think its the clutch.