Transmission Whining
 

I have a 2009 xd, manual transmission and for sometime now I've noticed a whining sound. It isn't loud but noticeable with the radio off when I'm in 3rd or 4th gear. If I take it out of gear the sound goes away and it comes right back then I put in gear. I took it to the dealership and they said its normal, which I find a little funny... I just want to know if anyone else has had the same issue and what they're doing about it? Thanks!

Is the whining sound the same regardless of temperature?