Stearing Problems Pls Help

[dai]

Hi i have a 2002 citroen xsara 1.6 16v lx this is a car ive had for over 3yrs and had no problems untill 3am on route to work driving at approx 20mph when i heard a noise which sounded like metal snaping, i looked over the car no obvieous signs of brakege or damage when i continue to drive to work it seamed fine untill i turn when some times it knocks violenty dose not happen all the time ive taken the wheel off and track rods and ball joint all fine no exseice play which leads me to think that it could be the cv joint any views would be most helpful as my wife is due to give birth in 2weeks and ive no car and what size is the hub nut thank you