I drove these and turned wrenches on them for years. I can't ever remember miring one to where we couldn't self-recover it but, hey, maybe I'm just blocking out bad memories!
We hung them up on stumps and down trees a few times though.
Airing down the tires and having chains on will usually let you drive through mud or wet snow with the belly plates dragging. Remember, there's no on board air compressor so be judicious in airing down. They generally don't like snow or ice, the thing just doesn't have the weight or tires to go in either. Chains though, let it handle both.
Maintenance is a pain. As stated, a lot of the time you really can't get at what need fixed, cleaned, lubed or adjusted. You'll spend a fair amount of timed contorted into pretty painful positions. You'll learn to work through access plates, drain plug holes and the like and you'll learn to work by feel, around corners while standing on your head or while draped across something hard and pointy.
With heavy use, cracks, self locking fasteners that won't lock and broken welds can be an issue.
The "carrier" (the rear cargo part) is thin aluminum and would likely need a plywood liner to haul firewood and the like. The end gate is thin aluminum and cannot handle ANY abuse, not even using it as a step or seat. Consider bonding a plywood skin to the inside to protect it. Later end gates came with the plywood skin.
Brakes can be a major PITA. The damn thing has 3,248 u-joints. (at least it seems that way!)
Leave a couple pairs of good hearing protectors in the truck.
There's a cross level line between the two fuel tanks so, if fueling it on even a shallow side slope do it from the uphill tank without removing the downhill cap. (Don't ask!)
There's no spare so be sure to have a "truss kit", it allows you to lock the tractor and carrier out of articulation so you can move a good center axle tire to an outer corner.
Swimming is VERY problematic. From memory, the max cross current is only a few MPH (3?), wave height is limited to 6 inches and if the tire tread is badly worn, you're not going to go anywhere in water. Approach angles are limiting and it doesn't like to crawl out up a muddy slope.
Follow the loading and weight balancing instructions very carefully. The tractor itself is so low in the water that adding a few special purpose kits, like the hard top, fuel fired heater, cab radio, winch, machine gun mount etc, make the truck a non-swimmer.
If the carrier isn't loaded the carrier sits butt end high and can swamp over the front edge. Swimming an empty carrier is asking for trouble.
The carrier end gate must be perfectly flat with NO edge deformations and the carrier end gate opening must be free of dents and distortions. The end gate gasket must be resilient and pliable to seal well. A thick coat of grease on the gasket helps seal it.
All the drain plugs and access covers must be properly installed, free from deformations and gasketed as appropriate.
The bilge pumps and thier hoses must be in perfect order. The screens must be clear. Put enough water in the hull to get up past the axle prop shaft seals. Before pumping out, park it where you can see any water leaks and leave the water in for a few hours to see if anything leaks Then test fire the pump.
When preparing for an assault river crossing or other water op, we used to load them and then "pre-float" them (away from the crossing site) with the only crew being an expeienced driver (who wore a PFD and could swim), no top on the cab or carrier (the kiss on death if it sinks) and a winch cable on the pintle to recover it if it sank.
Rescue divers in engineer bridge boats or rubber boats were ALWAYS on hand.
In short, most active duty units rarely or never swam the Goats. I only ever heard of one National Guard unit that swam them. Every other truck in the uits needed a ford or bridge so why go through the hassle and risk?
All this said, If I can find one in reasonable shape, within 1500 miles and can afford it, I'll buy it.
Lance