**Long and thorough explanation of a post**

Recently bought an 06 G35x 181k, I replaced all the fluids (OEM) and double checked their levels. Gave the car a good overall inspection of its AWD system and confident enough to drive it at highway speeds. After say 10 days of driving I noticed a vibration coming from underneath the midline of the car. It only happens when I let off the gas at about 65 and the speed decreases to about 60mph. It has brand new tires and a very good alignment.
I’ve checked forums about the front propeller shaft completely getting destroyed and mine is not bad to where it’s binding, however service manual calls for a 0.0mm tolerance in axial play of the u-joint of the front propeller shaft. I got under the vehicle and checked for any play to the u-joint but I didn’t have a dial caliper and I couldn’t produce any budge by hand unless trying with a pry bar but then again I’m unclear if I spotted a significant amount of play.
I’m not suspicious of an issue with the rear end because I would have picked those symptoms up at lower/different speeds and loads however I am open to discussing different experiences and opinions of what this might be. Also, what have you all noticed in drivability issues relating to worn bushings or the carrier bearings for the rear