So I purchased a 2020 Off Road Premium, up from my 2018 Off road, because I wanted to new features, radio blah blah blah. I live in Colorado, and had to start using the 4 wheel drive almost immediately. Noticed a whine, under deceleration, then to a howl/moan/roaring noise between 30-50 mph in 4 wheel high, under acceleration. Thought maybe tires, lifted the vehicle with the same kits they charge 12k for on the new ones they sell here, noise still present. Changed the needle bearing to the ECGS clam shell bearing, and noise is still present. Take it out of 4 wheel drive and noise goes away, take foot off accelerator pedal, noise goes away, over 50 or under 30 in 4 wheel hi, nothing. The vehicle now has 3500 miles on it, and I am set to drop it tomorrow morning for a resolution. I have driven so many 4 wheel drive Toyotas over the years, the is my third Runner, new one every 2 years as I used to work for Toyota, had three tacomas and a FJ Cruiser, and have had all of them lifted and never one single issue. I am super in tune with my vehicles, so this is disturbing, and I will go all the way up the corporate ladder if this doesn't get fixed. It is definately in the differential, as I can also feel it in the steering wheel and the floor panel under the driver side. I am not sure if this is the same as what you guys are having an issue with, but I will let you know what ends up happening.