transmission?

[frenchi971]

Hi,
I'm new here and maybe this subject as already been treated but I didn't see it.
I have a 2011 rogue awd bought from CarMax @ 38000miles. now I reached 60k
I did change the fluid in the transfer case and the rear differential following the very helpful tutorials on this forum(@ about 48k)
My concern is that I didn't do big trips before the fluid change and lately I went from Atlanta to DC and realize that when the car is hot (let's say after maybe 10 miles) I ear a high pitch noise when I go over 2000rpm.it sound a little bit like the noise of a worn clutch on a car with stick shift.
I just moved from Atlanta to Spokane and it did the same and I am worried.
Is this "normal" or do I have any damages in the transmission?