Just a update, gearbox and clutch removed, found radial springs broken and disc material near to rivets and breaking up.
Release bearing carrier screws all finger tight, one had the head missing and another head came off whilst removing, this is probaly the source of a another oil leak.
Decided to remove transfer box, just as well as one mounting bolt was broken, yet to remove the broken part from case, and been broken for sometime judging by the rust around the mounting, another was loose. As I now have another box, which requires work to two of the mounting bolt threads and also have the new bearings to repair box just removed, will probaly do the latter.
Degsy, it would be easier to use overhead gantry, but I do not have that option, although truck has 7 set fitted, I could always unbolt and turn around, have gantry over cab, now thats a thought............