1999 Land Rover Defender transfer-box issue

lack of oil or excess wear to shafts and sprockets.or a restriction in either diffs

Im assuming you have had several problems with this? Defenders only tend to suffer transfer box problems when they either run low on oil (EP90) or when the oil overheats (quite regular when towing)

If you are suffering from the latter problem I would reccomend fitting a extended sump to replace the cover on the bottom of the box. This are made by companies like rockymountain. This gives you increased oil capacity and extra cooling thanks to the fins on the new sump

Hope this helps