Electrical motor sound from transmission?

After I flushed the trasmission this weekend on my 2007 TRD sport, I heard something that I haven't hear before: With the motor off, but the key turned to the on position, there sounds like there is very quiet electrical motor runnning near the area of the transmission. Any idea what this is? Should I be concerned about it? I'm pretty confident that I completed the diagnostic routine with the AT Temp Lamp correctly as outlined on this forum in a couple of different places, so I don't think it's a low/high fluid problem or anything like that. Could I have screwed somelthing else up while doing the flush? I've driven the truck about 250 miles with no problems and no warning lights coming on. Any ideas would be appreciated.

 

sure its not electric fuel pump?

 

I guess it could be the fuel pump, but I've never noticed it running before when I turned on the key. Is that normal, or should I take it in to the dealership to have it checked?