when my truck is off and keys in accessory position (wait to start light) I can hear a motor running (sounds like a fuel pump) from the tranny pan. While this motor is running i hear an inconsistent tapping noise almost like fluid dropping to the bottom of the pan.After 20 sec, the motor stops running, the sound stops then it starts all over again. I cant hear this noise when truck is running. Truck drives fine.

Maybe this sound is not coming from the tranny i have been reading and it sounds like maybe a lift pump?

 

That would be a no on the lift pump. Our 12 valves are mechanical, so they don't run if the engine isn't running. I'm thinking the heater fan. Do you know where it is?

 

Where is the heater fan located? I have not had my truck very long so im uneducated about it.

my bad was thinking i had an electric lift pump.

My buddy was saying that it could be the heater grid relay clicking. Its hard to locate the sound but im pretty sure now that its not coming from the tranny

Does it make a difference if I dont hear the sound when the truck has sat over night? Only after it has warmed up

 

It's on the passenger side, pointing down at bottom of the plenum. 3 small bolts and a wire connector to remove it. It may have leaves or other debris inside the cage that you hear rattling.

If they are working properly the heater grid relays don't click on and off, especially if the engine is warm. You would see a corresponding rise and fall on your voltmeter if they are the culprit.