I have a 2011 Infiniti g37x Auto sedan(85000 miles). I noticed that when I shift into or out of reverse there's this clunking sound from the rear side of the car. this also happens as it shifts while driving. I only hear it in the low gears though. It could be that the road noise at higher speeds masks the sound but not sure. I tried to use my phone to see what is causing the noise but since its just me its hard to pinpoint exactly where to place my phone from the driver seat. So all I can really provide is the sound

 

It'll be coming from one of the rear axles, if you do some searching for axle clicking and a castle nut modification it will make it go away. Not uncommon on these cars.

 

https://static.nhtsa.gov/odi/tsbs/20...71195-0001.pdf