... once the car is warmed up the noise disappears.

Recently the car had a ztube and revup airbox put in, and also the windshield replaced.

Shortly after that the car went in for a 144k km service at a Nissan dealer.

Anyone got any ideas? I thought maybe something in the intake or something to do with the windshield (which is why I mentioned them first), but find it strange that it disappears once the car warms up.

 

the infamous whirring noise. . .if its very cold during the time when the sound occurs (below 40 at least), likely the transmission. some have had their trannies replaced due to thsi sound under warranty ( something to do with the synchros. . . r u grinding gears at all when you shouldn't be?), but others, like myself, was told it was 'normal'. so far, i have not had any performance issues, so i'm not gonna sweat it

 

Nah, not grinding gears, just had the tranny fluid replaced. Doesn't seem to impact performance... I guess I'll see what happens when I get back from Afghanistan...

 

I get the whirring noise... and it can be a biatch to shift under 3000 rpm. If I keep it in gear longer, it seems to get better faster. So from my house to the fist stop sign - 200 feet - I just leave it in first. Then 1/4 to the next stop sign, leave it in 2nd (25mph). By the time I reach that stop sign, everything is smooth shifting-wise. Definitely worse when it is cold like this morning. 4F.