Mitsubishi L200 noise coming from gearbox

hi i got a l200 and it came for clutch we replaced clutch kit brand new as the clutch was slipping ... !! as we removed clutch the clutch plate appeared to be new but heated at high temp eg .. changed colour by springs so we replaced clutch as told and wen we started the vehicle a terrible rattling sound as if the bearing is worn but its brand new ?????? and we moved it away from the presuure plate while running still same sound ??? it sounded to me like gearbox problem ??so we got a second hand one and replaced leaving new cluth on started it and sadly same sound as we done this car on the floor twice!!!!!! can anyone tell me before i take it off again if there is a common gearbox fault or do you think it wud be the clutch ????? also the noise was not visible wen vehicle came in i think due to slipping clutch so gearbox shaft connected to clutch was partially disabled helppp please ne one im tired lol thnx