Found this old post on the Land rover forum(2008 )

"On level ground, all six wheels have an even contact pressure.. But on any uneven ground, without compensation for the rear bogey, any one of the rear axels could be carrying more weight than the other.. If your going to make an effective 6x4 you must design a rear suspension that will spread the weight evenly between all the rear axels over all surfaces. Great examples of this are with the Sammell 6x6 which uses a rocking beam between the rear axels, giving full compensation. No one axel carries any more weight than the other.. Plus without this you can easily overload the axels.

On the Range rover 6x4 fire tender, that extra ''dolly axel'' is dead. In an off road situation Ive watched, a fully loaded range rover fire tender got stuck crossing a ditch between the road and a field.. Seeing just one front wheel spinning in the grass while the middle wheels spun helplessly in the air looked shameful. 6 wheels and none of them could drive. If only they'd fully compensated the rear axels and not simply added another coil sprung axel it would have worked.

So it stopped because once the front wheels crossed the ditch, as soon as the middle wheels reached the hollow and of the ground this left all the weight on the undriven axel. If the rear bogey was properly compensated then the weight would have been shared evenly between the rear axels..

Thats why compensation is vital if your extra axel isnt to become a plow".

This happened to me on some very loose soft ground before I knew anything about the Range Rover 6x4.Because of a slope the middle wheels were spinning so were the front ones. The rear wheels just supported the front spinners! We had to reveres back down the track to get out of this situation. Even Difflock made no difference.

Just thought it would be of interest to members.