Diff lock linkage i think?

OK found my Land rover 90 300TDI in Difflock. Weird i know, the gear lever says it out of Difflock the sensor is knackered so this is not a reliable witness. When i shove me hand into the gap on top of the transfer box and move the lever manually it pops in and out fine with a nice comforting click. When jacking up the front wheel spins round happy as day when out of difflock, and not when in.
The rear wheels are not the same just get about a 45 degree turn but not wound up which i would expect.
When i look under the little gear stick it moves the lever on the transfer box into Diff but does not have enough movement to take it out!
So the questions are..
is my transfer box knackered?
Is my linkage the problem?
Are my rear wheels meant to do that?
What the hell is going on?????
Is it going to cost me a bloody fortune?
Thank you on very hacked off truck owner.

just check plastic bushes are there and not to worn or adjust the linkage were it pivots on eye bolt keep the front wheel jacked up to test you have it right

Where would i find the bushes from what i can see at the moment its all just metal linkage can't see any bushes!! at all? How do i get to all this there must be a easier way than shoving me hand through from the access panel under the drivers seat. Finally the rear wheels are they all right?
Thank you again just seems one thing after another at the bloody moment! Could be selling it soon. About to have a £10,000 pay cut so will soon be screwed in more ways than one!

if you look down linkage ,bushes sit were it pivots ,were adjustment is made ,you need to undo to bolt were it secures to cross shaft 7 and 8mm spanners needed ,and remove pin through pivot to adjust