I could tell that the ride height changed when I put it in "Lo". I haven't measured it, but to me it was noticeable. Honestly, I agree with you that the range is not all that great. Plus, there is no telling where Lexus measured the change from. That's basically when you find out they meant 3-inches overall or some bogus marketing crap they come up with.
Regarding your question about maintaining the range, I have seen other forum members post things they did to trick the system into thinking the height needed to be higher. From what I recall this involved placing washers between the frame and the ride height sensor. Basically, the sensor is judging the distance between the sensor and the metal frame. By taping washers to the frame under the sensor, the system thinks it's leveled out when it is really not. I have not done this nor do I intend to, but this would conceptually solve the issue of maintaining a 3" ride height.
Overall, you're limited by the amount of height the airbags can achieve. Also, it would only raise the rear as there are no airbags in the front suspension. Firestone makes a decent airbag system for the 4Runner, and from what I've been told most things that fit a 5th Gen 4Runner will fit the GX460. The only downside is the system is manually operated, so unless you tap into the GX460's existing system I think it will be more of a pain than it is worth. I bet you Lexus claimed the 3-inch ride height because that was the maximum extended range of the airbag. I will measure it when I get home and confirm this. Or they could have measured it as 3" for high, 2" for normal, and 1" for low. Therefore, they can claim 3" of range when in reality it's only 1" up or 1" down. Ah man, now I am bummed out.
The bump stops could also be a factor. Just spit-balling, but once the air from the airbags is expelled there is a possibility that the height doesn't change much because the rear bump stops rest on the rear axle. Thinking about it, this actually makes sense as a possible reason. I had to change out my rear bump stops on my 4Runner to allow for more articulation when I use to go mudding. Also, you can only adjust the ride height when at low speed, which would make sense because if you hit a bump at high speed you could damage the bump stop. This is just a thought. I will confirm later.
Ultimately, Lexus designed this vehicle for luxury. Thinking of that, I am sure there are various redundant systems to maintain this luxury feel. For example, if the airbag were to go out the bump stops are probably beefier and designed to make the ride decently enjoyable until you can get your vehicle in for repair. They way I would attack this problem is to start from the bottom (no pun intended). By that I mean, I would first start with what height I want the vehicle to be when I am in the low suspension mode. Then I would work to adjust everything that tells the vehicle the low suspension height has been achieved. Kind of like that washer idea mentioned above, but in reverse if that's possible. I will let you know what I come up with. Yay, more tinkering for me. And yes it would be nice to have the height adjust automatically when parked. It would also be nice to have my mirrors fold in and out automatically too. I hear that feature just now became available for 2015.
Thanks,
_AC
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