2001 GU Patrol Front Auto Hub problem

Travelling home the other day doing about 100kph on the Hume a loud rattling noise started coming from the drivers side front wheel hub. I stopped and had a look but couldn't see anything obvious. Continued on the noise was gone, about 3 or 4 kilometres later it did it again, I pulled over to the side of the road and as I came to a stop there was a very slight clunk in the front end. I reversed to see if the front hub may have been still engaged as I had used 4wd earlier that day. Travelled the rest of the way home about 100 kilometres with no problem. Any ideas.