So I took my '23 P400 out to the Ozarks this weekend and tried out a number of the off road features. Everything worked as well or better than I could have hoped (went everywhere the built up Rubicons did), but I do have one thing that I'd like to look into, because it was quite frustrating.
I engaged in low range for a bit going up a steep, very rocky grade that had some level spots interspersed. The issue I encountered is that if I went more than 3mph, I'd quickly rev up to 3K rpm and hold there, never shifting. I noticed the same issue when I had it in a driving mode (e.g. Mud & Ruts) where the center diff lock was engaged. I most often wheel my 300tdi D90, and in the spirit of controlling my own shifting this weekend, turned to sport mode to make it up shift.
Has anyone else noticed this? Am I crazy? I feel like I should be able to drive 4mph in Low without the engine revving so loudly, especially in short level stretches.

 

Mud Ruts and Sand are both what I term to be "momentum conservation modes". The computer logic here is to set a high rpm level to ensure sufficient power is always available to spin all four wheels fully so as to clear away the sand, snow or mud in front of the tires. To do so, the computer mostly disregards your throttle inputs and needs control over transmission shifting to best optimize its torque distribution capability (experience teaches that the computer can match gear shifting to the tractive conditions much better than the driver, so manual shifting off-road is not the most effective way to go.)

These two modes are counter to the baseline old-school rule of 4WD which suggests that wheel spinning is to be minimized for any purpose other than to activate a limited slip differential which shifts torque across the axle to find a non-spinning condition on the other wheel. Instead, the new Defender can proceed forward steadily while all four wheels are spinning freely (or so it appears to the human eye). In fact, the power is being moved around very lightly and quickly to use every bit of traction available. A human driver in an old-school 4WD (which does not have fast braking on each individual wheel and edifferentials) is not capable of this.

I only use these two modes when there is more than 3 to 4 inches of soft surface (mud, sand, snow) between the tires and firm surface underneath. When in these two modes, the computer understands you are telling it that it will soon again experience the need for momentum, so it maintains elevated RPMs throughout. If it comes to believe you have forgotten yourself, it will flash a very stern warning on the dash suggesting that you switch to AUTO mode (implying you clearly are not serving as an effective partner at that moment). As an aside, it is quite a shock to be instructed by your vehicle in such a manner, the first time it happens.

It does take some time (several months) to learn (and accept) the new skills necessary to let the computer control those actions which the driver executes on an old-school 4WD truck.

Enjoy !!