Center diff lock is when you push the transfer lever to the left. It locks front and back so if (for example) back wheels are on slippery stuff, front wheels still provide traction. All-wheel-drive requires a diff for driving on the road (since the front and back will always rotate slightly differently, depending on exact tire size, turns, etc). It's okay to lock any time you're off road, but I tend to lock only when it's going to get slippery, like sand or mud.

2000-2004 Disco IIs don't have this (specifically, the diff can lock but has no lever to lock it; some can be modified).

 

Your 95 has the center locking diff here in U.S. know as
a transfer case.
Just one of them U.K. terms.
When you lock it you get a 50/50 power frt/rear
no matter what.

 

i wish my freelander had low range

<hangs head in shame>

-James

 

Spacers are one of the worst things to put on a Rover, especially when you are dumping them on top of a warn out suspension, good thing to not reccomend to anyone who is unfamiliar with 4wheeling.
Springs and shock and a couple of Rover riend to show him what makes his truck tick is what is needed.
Mike