Traction control

I have a 2007 4.7 tundra 4x4,that I purchase used with 82000 miles on it.I have notice that when I spin my wheels in mud I hear a noise that seems to be coming from under the hood when the traction controls kicks in.I do not have the 4 wheel drive engaged,is this normal,i have no other problems with trans or engine,just hear this noise when rear wheels spin.As soon as I hear the noise I let of the gas.Is this normal?what is it? Thanks.

 

Normal. Nannies are still on .