By the time I had finished doing the bits for the MOT yesterday it was getting dark. I had a look at the transfer box from underneath and there is a plug where the temperature sensor should be, its an allen key bolt and its a bit damp around it. There wasn't much fluid on the bottom of the box this time, just a little.
I also had a look for the temp. sensor below the top cover on the bulkhead. No sign of a temp. sensor or doctored wires anywhere along the top of the bulkhead. The only wires leaving this area go to the (I assume heated) washer jets. I also had a look down the back of the engine and could see no loose wires. There is nothing leaking from the top of the box where the breather and high pressure hose goes in though so it may be this plug where the sensor should be thats leaking.
I'm going to go and have another today while its light. I was also going to change the tx box fluid but a mate went in to get the oil yesterday from Vauxhall and they gave him Dexron II, which is for the PAS only?
Can anyone confirm this is the correct part number for the oil that goes in the transfer box - GM Part No: 90443530