it’s an electronic braking system using the ABS which in ice conditions is kind of dumb
On the contrary, using the ABS to maintain traction is smarter than using a locked diff, even in ice conditions. A locked diff will ensure that the slipping wheels will give an excess of power to the matching wheels and so traction will likely be lost on both wheels. Whereas break pressure can be adjusted proportionally only on the slipping wheel over the pressure range necessary to give drive to the other wheels. This works best if no diffs are locked. Sensors can tell when all wheels are turning at an appropriate speed. You just can’t do that with a differential – locked or not.
I think diff lockers are an obsolete boys toy, having a lot of folklore. If properly used, they are better than nothing on cars that have no traction control. Those who like to skid and drift hate the way traction control inhibits that, but that is what it is supposed to do, and 4×4 vehicles are not appropriate for that kind of fun. Now we have a much better engineered way of handling slippery conditions that requires no selection by the driver. The new way is likely to be better for inexperienced drivers in all conditions.
Land Rover tested this exhaustively and were so confident that they removed the diff locks completely on the highly off road capable fly-by-wire go anywhere Discovery II range. BMW followed suit with the same system (it owned LR at that time -1998). They have since had to make them an option for the gadget freaks who believe that they still need them.
Land Rover was working to a British Army spec that required the vehicles to be able to be driven in all conditions by off road inexperienced city boy soldiers – and while towing artillery pieces. That is also why they have hill descent control. They probably figured that these drivers would not know how to use diff lockers properly and would leave them on when not needed, reducing the safety , reliability and life of the vehicles. These assumptions seem to me to be about right also for urban North American winter drivers.
By no means do I think a locked diff is useful for ice driving. It only comes into play to avoid being stuck in a rut but once moving, only a fool leaves them engaged.
I don’t like the brake engaging traction control concepts for a vehicle that is losing control (skidding through a turn, etc). It just strikes me as a bad idea.
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