I have found out the problem it's my transfer box the small diff inside it has broken up Many thanks for all your replies

When it first happened I was at a pay and play site I remember going up a gravel hill and not being able to get up it as my front wheels were digging a hole so I came down and thought better go home as going home it was clunking jerking loosing drive so I put it in diff lock and it drove home...

I have changed both diffs for good ones half shafts splines are good No didn't feel any wind up When it clunks it like jerks as if the it looses drive then comes back and it happens in a straight line

problem of clunking loosing drive loud banging noises I lost drive totally put it in diff lock got it home I took rear diff out teeth were damaged and the rod connecting 2 cogs together was snapped Took front diff out the same so replaced both check half shafts and cv's all seem ok Put it all...