Well for anyone interested to know I started with the simple before moving onto to bigger and more expensive jobs as there were and have never been any fault codes displayed in DIS or INPA throughout this whole situation to guide me on where to start. I decided to pop into the local $tealership and purchase a 1L bottle of transfer case oil (AU$63) and then I set about replacing the easiest thing I could.

When I dropped the oil it was quite dark almost black (new oil more like honey) and had a slightly burnt smell (new oil was sweet). Once it was filled with new oil I got the laptop out and reset the VTG adaptations on DIS then went for a test drive. To say there was a difference is an understatement! During the first 'power' run it had a very slight shudder in first but considerably better than it has been for a long time. By the time I got to number 4-5 'power' run (time for the oil to circulate etc) the original problem was pretty much gone and it was back to normal. Each run it was getting better and better.

Hopefully that was the cause of the problem and it doesn't come back for a long time!