Diff noise maybe?

Hi All:

2011 4x4 auto with a 2.7. Last year I went to 4:88 gears.
Lately I have noticed a noise from what I think is coming from the differential.

At freeway speeds, I can hear what sounds like marbles rolling around in a tin can.
The ONLY time I hear this noise is when there is no load on the drive train. Not when accelerating or completely off the gas and slowing down. Only hear it when I "rev match" for lack of a better way to explain it.
Any idea what I might be hearing? No abnormal noises any other time.

Thanks

 

Anyone?

 

Try greasing your drive shaft through all zerk fittings. I had some chatter coming from the same area. IT went away after I greased. The drive shaft does require greasing at fairly regular intervals.

 

Catalytic converter breaking up inside.

 

Okay well it sounds like the diff is not the culprit.
I am getting the converter replaced next week because of the recall. I greased the u joints 7k ago but will do it again.
Thanks for the feedback.