Transmission noise?

[Bob24]

Shortly after I got my 07 M45 I started noticing what I thought was an exhaust issue. Sometimes under acceleration I would get this sick whirring noise (imagine a the sound a paper shredder makes).

I thought that it was related to the exhaust and when the car was in I asked the dealer to look at it. They couldn't get the vehicle to make the sound so nothing was done.

I put the element exhaust on and as a side effect I was hoping the sound would go away. It didn't. I was still operating under the premise that it had something to do with my exhaust.

Now I am not so sure. I think it may be the transmission making the noise. The drive belts were just replaced so that isn't the issue and I initially noticed the sound at 20k and now the car has 27k on it. Would this be to early for any transmission trouble?

Anyone have any ideas what it could be? It doesn't make the sound all the time and the only time it happens is under acceleration.

[Zamba]

I began noticing a slight whining noise while accelerating in my 06 M35 about two months ago. It's fairly quiet, and I have no idea where it comes from.

[Poyzinous]

The RE5 transmission is practically bulletproof, so I wouldn't make that my first choice for an issue. However, when engaged, i've noticed many A/C compressors whir as they actuate and increase under acceleration. Unless the noise becomes loud, or something fails, I wouldnt worry so much about it...