a bit of help?
 

what happens to the car if you rase the hight of the front diff/gear box on a 4wd? i understand in genral rasing the height will make the car more stable and should help landing on power am i right?

do you mean raising the ride height?

no rasing the diff outdrive in relation to the chassis eg the pred diff is allot higher than the xx4 diff

Schumacher have this to say...

It is possible to run the cat with the diff in a high or low position, when running on tracks with large jumps using the diff in a high position causes more drive shaft plunge. The added friction of this can Help make the car more stable on landing when under power. This setting could also help with traction on loose surfaces. On normal tracks we would recommend running the diff in the low position for reduced driveshaft friction.