Ground loop

[skivir]

Ok. I am having a high pitched noise, aka whine, come out of my speakers. I've done a lot of research on a ground loop. But what I am learning doesn't go with my situation. My 05 Explorer does not have a system in it. I just bought it, so I can't say if it ever did or not. When I bought it, it had the stock radio in it. Had the wine then, put in a Pioneer CD player in it so I can have an AUX input. Still have the whine. I have connected the ground wire from the new player to the ground wire in the harness, whine. Grounded those two wires to the chassis, whine. Disconnected the two from each other, and grounded the unit directly to the chassis without the harness ground, whine. I have pulled the door panels off, all four, and the speakers and wires all look good there. Also, my whine is affected by my RPM's. However, here is an oddity I can't find info on. If I am not on the gas pedal, no whine. If I am 'heavily' on the pedal, no whine. It's when I'm maintaining a speed, any speed, from 5mph to 80mph, is where the whine is. Cruise control on or off, whine. Radio on or off, whine. The higher the speed, the higher the whine. I am to the point of taking the truck back because I am already prone to headaches, and I can't handle getting one everytime I drive. I do really like the truck, and want to keep it. Got a great deal. 85000 miles, clean carfax. Only paid 8750 for it. Anyway, all the info I'm finding on a ground loop applies to if you have a system, which I do not. Thanks for any help.