Without wishing to sound too desperate, any advice at all would be great. Although the wheels turn alot more freely from the front box than the rear, there does seem to be some friction at a particular point of the rotation. So, when you turn the left front, part of the rotation becomes stiffer, thus causing the right wheel/suspension arm to lift.
The rear wheels seem particularly stiff. The only point of reference/comparison I have is my grasshopper and when I turn one of the rear wheels on this there is virtually no friction/stiffness at all.