differential whine
 

I've recently noticed that if the car is in gear and up to speed and i am pushing the gas, a faint but audible constant whine comes from what appears to be the differential area. Not sure if this is a new thing or has always been there since I usually drive with windows down, music on, etc... and the sound is faint enough that the music has to be off and the windows closed to be heard. The sound goes away if i lift off the gas, and happens again as soon as i get on to the gas pedal again.

Topic is well documented - search for whine. Last I remember it was suspected to related to the fuel system?

I have noticed this noise as well. Only happens when Im at speed and then start accelerating. If I take my foot off the gass it goes away. Its not like the high pitch ECU noise that everyone seems to be complaining about. This sounds like supercharger whine, or an over tightened accesory belt. And no, I have not installed an S/C nor have I messed around with any of my belts. Anyone?

Hey my 2001 Jeep Cherokee has that same exact problem. It's a stripped gear or something because I apparently was driving it around with no diff fluid in the rear.

You better check your fluid levels before it gets worse

Does it almost sound like alternator whine? If so it is definitely well documented here.

Air intake?

The alternator whining thats been documented so far on the site concerns electrical interference with an after market sound system/speakers, usually due to poor grounding points. This is not the type of whining I'm hearing. I really don't think it's the differential fluid as I haven't seen any signs of leakage, both on my driveway or on/around the diff itself. Also, the noise is only heard when I press the accelerator. If it was the diff. I'd be hearing the noise all the time, no? Someone mentioned the fuel pump, and that they can sometimes be a bit noisy, but I'm really not sure. Maybe this is just the way the car is supposed to sound?

In my opinion, I would still check and change the differential oil. From what you describe, it sounds like it could be a low oil condition in the differential or drive gear misalignment. It's possible that it could just be transmission gear whine too.

You have checked your differential and transmission oil levels since you purchased the Z?

If your from the 350 site I fail to mention, on purpose, I know that this not your first experience with Nissan's.

I know my transmission does whine a bit and I plan to change the oil to a better quality of oil to help the gear whine, among other things.

did you ever determine what the sound or problem was?

This is reviving a dead thread, but a whine from the rear may just be the fuel pump. It's quite noisy, especially at startup.