This disco has never been off road. So I don't use 4wd low gear. The other day I tried to shift it into low gear, it won't move. Any thoughts?

 

That’s a fairly common problem with D2’s that don’t go off road. Due to lack of use the Hi/Lo shifting mechanism corrodes and seizes up. You probably need to remove it to work on it to free it up, or if it’s bad enough, to replace it.