I recently purchased a 2010 g37x sedan. I love the car but it has something wrong. Any help would be appreciated! It’s a booming sound and a vibration once it achieves about 60mph. My mechanic got it up to 90 and put it neutral to coast, the sound and vibration continued. So far I have replaced:

-wheels/tires with factory wheels and tires to match, it was also balanced and aligned by Infiniti dealership.

-three of the four wheel bearings have been replaced

-new brakes and rotors

-installed a used transfer case

-installed a new front and rear drive shaft

but with all this works trying to figure out what is happening, it still isn’t right. Has anyone dealt with this problem before?!

 

There's a TSB out there on this issue. Iirc, the procedures is to "free up" the rebro joint at the rear propeller shaft. Just unbolt, replace with new hardware.
Not sure how this fixes it..