Land Rover Repair: transfer box, diff lock, mover system

Question
I own a tdi Disco 200 1994 vintage. At present it will not stay in low either diff lock or not. After a while I have finally got it to stay in high diff lock. Might this be because it has never been off roaded ever and I suspect never been in low ratio. Could you give me an idea of the solution before I start to tear the thing apart.
Cheers John

Answer
I'm afraid it will be rusty.

Yes it oftenly do that because the rare using.
You should try to spray well the mover system with some lubricant. But if its not helps, you must take off the transmission and trasfer box engager levers, and try to disassemble the engaging system.