Front axle noise in 4WD??

[TASR12]

Some advice please. When I put my '96 3.0td in 4WD I get a clicking noise in the front wheel(s). They are driving as it gets me out of the mud but it doesn't sound great! The wheels have freewheeling hubs on from the previous owner so I only engage them when I need them - could these be the cause?
I also get the usual noises on full lock despite greasing the stops so I think that will need investigating soon as well.
Any info on the first problem would be gratefully received.
Cheers.

[TonyN]

Its normally a CV joint. But I did have a Manual hub with a broken tooth on my old pickup that clicked every revolution when engaged.

[TASR12]

Cheers Tony. I will try to disassemble and see what is inside.....not quite sure what I'm looking for but when I get a minute I will have an explore.