I am new to Land Rover owning an H1 Hummer. My wife wanted a DISCO so I purchased a 2004 with 60,000 miles and it is great. I does have the 3 amigos but only on occasion and I will deal with that later. I have a question.
I am confused about shifting in and out of the differential lock The manual states move the gear lever to left from H to L. To disengage move the gear lever to the right . I have tried to move it to the right and left and it won't budge , it only moves forward and back. Am I missing something? Any help would be appreciated

 

Assuming you have a Disco II...
The differential lock is only available on some vehicles. On those without it the lever will only move forwards and backwards, between high and low range, leaving the diff unlocked in both ranges.

 

The 2004 should have the cdl. Take a pic of the shifting diagram behind the cdl shifter.
Could be it is stuck. my sons works better when barely rolling, if i recall.
left forward and back for normal low and high
right forward and back for locked, low and high.

try shifting it while rolling slightly.

 

i assume your shifter handle on an 04 should look like this picture.
it is quite possible that the cable has froze up from not being used.