Crossing a ditch
Set the vehicle up in front of the ditch, angled at approximately 45°. Provide for a sufficiently wide exit zone.
Lock the central differential and the rear axle differential where possible.
Cross the ditch very slowly in low ratio 1st gear using a very light throttle.
If the vehicle is stopped by excess articulation between axles, reverse.
Start again, taking a different line.
Accelerate hard to give you momentum to cross the ditch.
Ease off on the accelerator and let the rear wheels cross.