The scanner arrived a few days ago so now I'm trying to chase up an old laptop with XP on it.
Yesterday the Transfer case actuator gear arrived so I got to installing that.
Quite a quick install, and given the state of the old one and the fact I've drove it for 40 or so K's and had no warning lights, it looks like I might have fixed the issue (fingers crossed)
Thanks for all your help
Matt

I took some pics of the old one to show the wear but I can't post pics in an already active thread for some reason?