blackwolf wrote:

Usually this is because the selector mechanism has atrophied through lack of use and consequent lack of lubrication, but remedying it is not necessarily straightforward since it depends on which part has atrophied.

The first step is to get underneath and ensure that the external linkages are moving freely and fully. If they're not, you've probably identified the problem, and judicious application of lubricant and moving the linkage may solve it. If the external linkages are moving freely and fully and you still have no difflock, then it is overwhelmingly likely that the selector fork has seized on its shaft in the transfer box.

It is possibly (but extremely tricky due to poor access) to deal with this with the transfer box in situ if you remove the access panel (7 bolts on the nearside face of the front output housing of the transfer box) and lubricate the shaft and fork and manipulate the fork manually.

It is sensible to operate the CDL fairly regularly to make sure that it remains free and lubricated especially on vehicles which do low mileages.

Lady landy wrote:

Any joy sorting this out I’ve got the same issue