One of those questions...

[Scupper]

I am getting an intermittent whining noise (sounds like a small electrical motor) coming from near the drivers side rear tire.

This is where it is most audible for casual listening.

It is most noticeable after longer periods of travel.

2000 GMC Yukon XL.

What's your best guesses...?

[Macgyver55]

Fuel pump getting noisy......?

[Scott K]

Does the noise get louder at higher speeds, or is it there all the time, parked, and driving? Does it get louder under accel, or decel?

[Shack]

With out hearing the noise, I would have to say fuel pump also.

It sounds by what you posted, the veh. is parked and you are going to the wheel well.

This is with out hearing the answers to 4EW's questions.

[Jeremy airjer W]

I'll fourth th[e fuel pump.

The only time you have to worry is when you do not hear it!!

When was the last time you changed your fuel filter. It probably will not quite it down but it could be the source of the problem. They all make that noise at some point so its nothing really to worry about unless, like I said, you don't hear it.

[Scupper]

The noise is not there when I start the vehicle in the mornings or after sitting for a few hours. The noise does not increase or decrease with acceleration use.

I have not changed out the fuel filter in some time and will do so at the next oil change.

She is a good old horse with about 150,000 turns on her.

Thanks for the guesses as fuel pump was my initial thought...

[fishing tech]

Fuel pump noise may get louder as you burn off fuel. A full tank will dampen the sound a bit, plus the pump will get louder as it gets hot. Quick way to check,and you can do this with most engine noises also. Start it up or leave it running when it is making the noise, take a stethiscope or if you don't have one, a long piece of metal( socket extention, screw driver, or metal rod) put it against the tank or whatever you think is making the noise, squeeze it tight in your hand and put your ear against your hand. You will hear the same noise or not. If not, move it to another place on the vehicle where the noise seams to be coming from. Be sure to check a few more place once you locate the noise to pin point it. I hope this helps, I have done it many times this way out in the field.

[Macgyver55]

Or, when it is making the noise, have someone else shut off the truck while you listen. If it is the fuel pump, it will normally run a few seconds after the engine is shut off.