For the situation mentioned by the OP... a specific icy impassable stretch of steep road...
Low range, locked center diff, locked axle diffs if ya have them. And most important. Chains on all four tires. More important than any other factor. Chains on all four tires.
I have seen the newer ATRACs systems do a pretty impressive job of preventing wheel spin while still letting you build as much power as it could keep delivering to the ground (as opposed to the first gen which cut power terribly) and if you are just trying to negotiate a very icy hill in your rig, this is a big advantage. If you are trying to drag anyone else up the hill with you, not really a good thing though.
Just to clarify... you still want chains if is is truly icy. Just saying that ATRACs *can* be an additional positive factor.
I have dealt with situations like what you described above more than once with different '80 series rigs.
Chained up and pulled rigs out of the ditch like it was child's play, even as emergency vehicles were sliding down (what was hardly even a hill but was as slick as oiled glass) and narrowly missing me. The reaction of the cops and others watching who simply did not understand what lockers and chains can do was fun to see.
Drug a State Trooper's cruiser back from a halfway over a cliff scenario once after he slid of a road that sounds a lot like what the OP is describing. He was the last house on the road and called me early in the morning hoping to avoid having to tell the dispatcher exactly why he was gonna be late for his shift.
Chained up and drug multiple rigs up a hill to clear traffic blockage so that a (chained up) sand truck could get through to try and address the problem.
On another occasion, an F350 crew cab had broken through a frozen pond with the front axle. Frame sitting on the ice and the front driveshaft bent. I dug 6 inch deep trenches in the ice as I spun the chains dragging him out, but there was no question that he WAS coming out.
Modern studless tires are really good. I like 'em. A lot. But if you are on actual ice and hard packed snow, studs are still better. Make that call based on the conditions you will see with the rig.. Some of us in the US do actually see significant ice and snow on the roads that we travel throughout most of the winter. I run studless and studded tires on different rigs myself and appreciate the positives of both. Again, make that call based on the conditions you will see and what is best for your safety. Personally, not dying in an accident is a bit more important to me that any accelerated wear on the road surface that my studded tires might cause.
I have found that 2nd gear start is more apt to be a negative in icy conditions than a positive. Perhaps if you really have no idea of how to drive it *might* help a little? Sometimes? Someone who made decisions at Toyota thought so I guess. In my experience it is a detriment to a controlled start from a stop as well as continued low speed movement. It is akin to heading up a steep obstacle on the slick rock of Moab with a rig that does not have low enough gearing. You have to apply more engine power to achieve the same "push" at the tire/surface interface. When traction is lost, the engine and drive train want to spin up quickly to a much higher speed. On slick rock this causes bouncing, hopping, tire spin and breakage. On ice it causes slipping, sliding and loss of control. Not as dramatic as a rig bouncing until it spits out a ujoint, but it still ain't getting you going in a smooth controlled manner
The only thing I use 2nd gear start for is when I am off road in low range in easy terrain and I just do not need any gearing deeper than 2nd for most of it, but there are occasional short stretches where I want more and I do not want to have to stop and shift into low, or grind the TC by speed shifting without stopping. I never use it on icy roads.
But regardless of what kind of tire you use, when it is too slick to stand, much less walk... chains will get you through. Nothing else will come close to matching them. I keep a set of coveralls in the rig during winter season. Once I open the back of the rig, slip into the coveralls and lay hands on the chains, I can hit the ground and have all four corners done on an '80 in about 5 minutes. Have them off in less.
For an icy hill that is leaving people stuck at the bottom, in the ditch, on their lids...
CHAINS!
Mark...
