Ben - it's variable-pressure (via electronic control) - it never fully locks. I suppose you _could_ wire up a potentiometer + relay.
Garry - found the person who did a retrofit in the UK - turns out he _was_ finally successful and _did_ use a Faultmate!
If you go to:
Disco3Club The Discovery 3 and 4 Owners Club • View topic - Locking Diff retro-fit
you can download the PDF's explaining how he did it. Apparently cost him around 650 GBP.
Cheers,
Gordon

