Was I wrong in quoting the gear box codes LSD came in?
No, although I find it hard to believe a ZF was ever installed in an auto stick. I have seen a DD Type 3 gearbox mit ZF. My earlier short statement was that no particular model ever came stock with a ZF. The ZF was strictly an option. By far, the vast majority of ZFs were installed in Type 181s. But that does not mean all Type 181s have a ZF, they don't.
Are there any pointers you could give a novice like me on what to look for when i get it out of the box.
Once you get it out and apart, you will know what's wrong with it.
There are 8 low profile socket head screws holding the whole diff together. If you use a simple L shaped hex wrench, I guarantee you will destroy the bolts. You must use a 3/8" drive 6mm bit. Best is to drive it with a T-handle so the bit does not roll out of the socket.
Before you attempt to unscrew the bolts, first take note of the large centerpunch mark the factory applied immediately adjecent to the counterbore that locks the head in place. You must use a small chisel to undo the displaced metal. If you don't, I guarantee you will destroy the bolts.
Everyone I have been in contact with who has attempted to undo the bolts without following the above has ruined the bolts. Since I developed that procedure, I have not damaged any bolts.
When you get it out of the gearbox, read off the ZF part number and post it here. That will tell me which version it is. The ZF part number is 10 digits long, starting with 4061 001