Around 70 mph, if i press the accelerator slightly, or decel from 75mph there is a high pitched noise that comes from what sounds like the engine compartment......any ideas???? it's very annoying.

 

i get that same annoying noise, except mine is between 80-85 mph. i was hoping maybe it was air coming through the windshield wipers, but i turned them on and it wasn't that. not like my dealer will be able to figure it out....

 

I have this sound you talking aboout. Everytime I accelerate I will hear it. Brought it to the dealer but they can't find out what it is. Today I start my car, open the door and press on the gas. I hear the same sound coming out from the engine area. I listened carefully and found out that the sound is from my CAI sucking air or something. Hope this help.

 

It's been discussed multiple times. That sound is your throttle body opening, everyone's got it, but not everyone notices it.

 

i know what you're talking about but it's not my throttle, i know that sound. this sound is only around 80-85 mph and it's as if someone took a tuning fork and stuck it right in my ear...it's almost as if something isn't sealed right on my car and air's coming in somewhere. it's very ear piercing and of course, unless the dealer takes my car out on the highway it won't be reproduced, but it's ANNOYING AS S#$%!!!!

 

exactly...it's not the CAI. It only happens when i just barely have my foot on the accelerator. Therefore i figured it was something related to the drive by wire or something. But I hate it. 70 is cruising speed and i can hear it constantly on long trips...

 

I just posted in the other thread. I'm pretty sure I have the same thing (70-75MPH). Does it sound like the warning tones they put on TV during the color bars?
Mine started at 2500 miles. I'm quite sure it's the differential. Mine only whines under light load (flat ground, steady speed). This is the same crap I got with my old 1-ton van...it had 4.11s, so the rear end was really spinning. Dunno what the Z has in it, maybe 3.76s?? Might be close enough...
New (different) oil might fix it...but it shouldn't be long before Nissan figures it out.

 

This has been answered months ago. The Search function is your friend... but to help you out in that regard, the answer is the differential makes the whining noise.

 

Why does it only do it under slight accel/decel...and it sounds like it's coming from the engine compartment, not from the rear. It seems like if it were the diff it would only make that sound when you were turning the car.