I purchased a 2013 Pro-4X 5AT last fall after being without a vehicle for some time. I had a first gen X in high school when I was younger, and was drawn back to the XTerra now as an adult. My 2013 has about 87k miles on it now (put about 4k on since purchasing it) and I recently had to replace my rear axle seals and bearings (along with the rear brakes) thanks to a worn seal on the right rear axle. This repair cleared up some issues with vibration at stops, as well as at highway speeds. The rest of the drivetrain received a clean bill of health (minor metal filings in the rear diff, standard wear type of stuff). Nonetheless, I am paranoid about my baby as any parent should be.
I've tried to do a fair bit of research to see if I could track down the answer, but YouTube, Google, and various forums haven't provided a clear answer. My "issue" is related to a sound that seems to come from the transmission when revving the vehicle in Park or Neutral. I'm not talking rev limiter stuff here - more in the range of 2k to 3k, tops. As the revs die down, I hear a sound - it's not quite a whirring, not quite a whooshing, and not quite a rattling. It only presents as the revs die down, and only in Park and Neutral (a low rev brake test in Drive results in no sound, and normal load in Drive also doesn't appear to result in any sound).
Can anyone point me in the direction of what might be causing this? I'm trying to remember if my old Maxima or Altima (also automatics) made similar sounds and it's just an inherent part of automatic transmissions, or if I should be concerned.