I took my 4Runner to the dealer for its 15K maintenance and this groan/vibration issue. I had a very detailed discussion with the tech that included a mention of the TSB, that I could feel/hear the groan/vibration specifically at 38-40 mph in my foot (not the steering wheel), that the groan/vibration was repetitive (not a steady groan of large mud tires), that it went away in 4WD, and mentioning this forum discussion. I also mentioned that it appeared to go away during warm weather, which is the only point inconsistent with what others have mentioned. Because this issue was previously checked by the dealer and the other tech could not detect the groan, this tech had to involve his service manager — thankfully, the service manager confirmed the sound and authorized the NEEDLE BEARING repair. Luckily, they also had the necessary part and made the fix.
No groan/vibration — so far.
Special thanks to Catrains for his insight on this issue in the other post and here!