Also, did you actually notice your LX go into the "extra high mode" when you engaged low range while in H? I tried it and the truck definitely didn't move. Do you have to put the truck back in park for it to go up higher?
'Extra High' mode only occurs when:
1. The vehicle is in Low Range.
2. AHC height is already set to High Mode.
3. One or more wheels 'free wheel'.
(The vehicle senses the speed difference and assumes you are 'stuck' on something or motion is being impeded because the body/frame are in contact with something.)