Outer Limits 4x4 Board

hi all i have a 1983 LN65 hilux,all of a sudden it has started making a really loud clunking noise from around the g/box tailshaft.
the gbox was only put in about 2 months ago and has done maybe 500ks and has never made a sound.the noise increases with speed and goes away at low speed. it remains with the clutch pushed in and out
the centre bearing seems to be in ok condition and does not have much play.
any help would be great as i cant driveit until i get this fixed
cheers
rob

remove tail shaft n test the g box only or

put the rear end up on stands n test the drivline

check unis too or take it to a mechanic