Hi  , does anyone know if it is OK to switch to 4x4 from 2 wheel,while you are moving and back again at speed. In the book it says stop,but a friend of mine who has a x8 says that you can change on the move,any help would be great,thanks

Go by the book. The gears are moving and the little arm in there may break if it doesn't ketch just right. Look in the service manual on how it's put together and show your buddy. He might change him mind on that.

Hello, always stop to switch from 2x4 to 4x4 as well as blocking the differential, there is a lever arm attached to a plastic dent slider. This will be damage if the front diff is turning with different rev than the rear. If you are driving in a flat hard surface and all wheels are turning at the same speed it should be fine to cuple the 4x4 but not recommended. When you are on the road or mud and wheel are spinning differently, you will brake or damage the sliding gear that engaged the 4x4.

[2015 Z Force 800 53/Trail EPS]

You can without damage if:
1. You are under 12mph and
2. You are not turning in either direction and
3. You are not on or off the throttle..ie not applying power or decelerating.
Once done always flick/tickle the throttle to ensure the coupler is fully seated before applying full power.
Do this every time, otherwise follow the instructions in the manual. Like Cosmosdan says, look at the manual to get a good understanding of what's happening and how it works. This is a good idea for everything.

Thanks for that lads,will stop in future to change from 2 to 4.