Link that AceRider posted is indeed very informative. LR4 uses what is being termed
full time 4WD LR4 has an electronic locking center diff and optional locking rear diff (included with Heavy Duty package), but there is also electronic traction control to limit slippage at each wheel. So it is full time 4WD with added functionality of AWD systems (think Audi Quattro). I understand that the LR system is "different from anything else on the road", but I haven't found any clear explanation of what that means (asked several sales guys...). The diff locks are computer controlled (no way to manually activate). The computer control works very well, but I sort of wish there was manual override.
- Plus for auto: You can forget about it and it works perfectly 95% of the time. Display shows when each diff is open or locked.
- Minus for auto: When trying to blast through a snowdrift in an icy field (or a large mud hole, etc), I want all the power I can get and would like to lock everything BEFORE hitting the snowdrift, not when the computer figures out that wheels are slipping and need more power. I know what is coming, so could be proactive if allowed; computer only knows when a wheel starts to slip, so it can only react.
Bottom line: This system works far better than anything else I have driven.
LR4 also has a traction control system that uses brakes and engine control to limit power when a wheel slips. This is great on an icy road, especially with an inexperienced driver. Fortunately, it can be turned off; sometimes you WANT wheels to spin (for example trying to climb a snowy or sandy hill).
I have HSE with HD package so locking rear diff in addition to the standard locking center diff. See my post from a week ago about pulling 1 ton Chevy dually out of the snow, and then breaking a path up a field for him. I can confirm that all 4 wheels get full power (all 4 wheels aggressively spinning and throwing snow). This is distinctly different from a LSD configuration 4WD or open diff common in AWD.
I also have a 2002 Toyota Tacoma (part time 4WD) with push-button locking center diff and locking rear diff (factory); front diff is open. It is really amazing how much better the LR4 powers through snowdrifts, even though the Tacoma has much more aggressive tires. I've never driven anything that handles close to the LR4 in deep snow...although even the LR4 needs a tug when the driver comes into a snowdrift hard enough to get high-centered with all 4 wheels in the air!
My wife drives a 2009 Audi A3 Quattro (AWD), which I have also used in deep snow (even trying to pull out a small truck - that didn't work so well

). A3 uses an AWD system; as I understand it the computer applies brakes to the wheel that is spinning in order to limit slip. It works very well on icy roads, but not so well on a steep unplowed driveway.