I was at a supercharger this evening, and I decided to try Ludicrous + mode (since supercharging would heat up the battery anyway). I haven't had a prior opportunity to wait an hour for the battery to heat up, so I haven't really used it before. After I left the SC, I had a significant amount of freeway driving to do, so I left Ludicrous + mode engaged so I could watch the power numbers. As it turns out, the P100D is often a 2WD car. It seems that the Model S uses torque sleep whether or not one is in Range Mode, and torque sleep can shut off either the front or rear motors. When I wasn't in Range Mode, the rear motor alone was active if power needs were low and speeds were on the lower end (~50 miles per hour or less). Once speeds increased, the front motor took over and the rear motor went to sleep. If power requirements went above 60kw or so, both motors woke up and were in use. In Range Mode, the power threshold for both motors to wake up went up and the rear motor remained asleep at both lower and higher speeds (as long as power requirements were fairly modest). So, it seems that when Range Mode is off, the Model S is RWD at lower speeds as long as power requirements are low, and then it becomes FWD at higher speeds. The power threshold for both motors to wake up is lower with range mode off. When Range Mode is on, the Model S is either FWD or AWD. There were no scenarios where only the rear motor was active. The power requirement necessary to engage both motors was also higher. I apologize if this is common knowledge to everyone. I thought it was super interesting information, and I was fascinated that the car shuts off different motors in different scenarios. My prior understanding of torque sleep was that it was only utilized in Range Mode and that only the rear motor was deactivated. I wonder if 8.0 led to some changes in the design of torque sleep? I also wonder if torque sleep acts differently with P vs non-P models. I wish I could have taken some photos/video, but only me and my cell phone were in the car, and I couldn't safely drive and take video at the same time! Next time, I will have to do some more experimentation both on and off the highway. I could see a sharp turn causing the rear motor to wake up sooner or to shy away from a FWD bias. Issues with slick roads or other traction challenges would also likely make a difference. I will say just one more thing --- as I was driving, I would enable and disable range mode and the power display would instantly show the car switching between using the rear motor only to using the front motor only. This switch was 100% imperceptible as was any switch from a FWD/RWD to AWD mode. Tesla did an amazing job managing the use of the motors in the D cars!