A few days ago I noticed a new sound when downshifting. It's kind of a whirring/purring sound. Its definitely hard to describe.

It seems to be present in all gears, but is most noticeable in 2nd and 3rd but only in a certain speed/rpm range. Its present when downshifting, but also if I cruise at a slow speed.

I checked the level of my transmission, it was a bit low so I topped it off. Transfer case and both differentials were also full.

The only thing that happened before the noise was the placement of new shocks. Doesnt appear that anything is rubbing.

New to all this and trying to figure it out as I go.

[YOUTUBE]b0alNpJx1Kc[/YOUTUBE]

 

It is difficult to tell from the video, but if you think it is drivetrain related then try checking the U-joints. It sounds like a fast-pitched vibration, which points more towards U-joints and differentials than tires. You should remove the driveshaft to check the U-joints unless they have obvious play in them.