I can't see how you'd get it to fit under the vehicle when you're down to the door sills in mud. Single-stage hydraulic rams all create this problem - they are either too long to fit under when the vehicle is bogged down, or they are not long enough to lift high enough. So a 300mm jack (or piston) needs a minimum 300mm of space under the jacking point, and then raises the vehicle by a maximum of 300mm. A longer jack gives more lift, but needs more space.
Multi-stage hydraulics (pistons within pistons) might partially get around this problem in principle, but they start getting pretty vulnerable in lots of ways, and there are snags with the variable pumping ratio.

I like the thinking, though - for bigger trucks, what about using the hydraulic stabilisers they use on cranes? If one mounted suitable brackets on all four corners of the truck, one could use a pintle to position the ram as low as necessary, and then get a full piston-height worth of lift.

Rams don't generally like any sideways forces, so that might be a problem in real-life situations... Luke or someone will give a bottle of Champagne for the most elegant solution

Travel safely,

Michael...

somewhat delayed answer to the question as I've been away, 'what kind of ground was it?' it was concrete but the foot of the stand was only about 2 inch from the edge of the concrete which crumbled. Lifting a 3 tonne 101 ambie on a high lift is bloody hard work and, as has been said, putting that much effort in seems poor H&S practice as the whole thing becomes rather unstable

toyota landcruiser
landrover 101
ford escort and morris minor traveller!!

Both have their strenght and weakness. I live in a very rural mountain area where people own 4x4 to use, not as a status symbol. I ran into a guy that uses his hilift all the time to pull out his vehicles. If your going into the wilds be prepared and carry both along with a shovel, chain and possably an axe depending on where you are.You don't need a lot of fancy equiptment, but some basic tools and know how to use them. Practice hooking up your vehicle and pull it a litle from the front, rear and sides before you need to. That way you will know where to hook into your frame from all points. Also you will know if you are missing anything you need like shakels etc.

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John