Sound from Transmission?

[MuDDoG]

I dont know if this is the right place for this... when the car is on but not moving .. i get this vibrating sound.. its like something is lose and just moves ....
today i went under the car to see what it is .. and if i can fix it , it was comming from my Transmission... maby 6months ago i had new transfer case put in .. maby something got loose???

is my Transmission going bad ??

 

[TPLYNCH]

You sure it's the transmission and not a loose catalytic converter heat shield or exaust hanger? Check those first...