Ok when i start my truck and let it run for 20-30 secs it starts to get a high pitch whine. It aint really loud but it's very high pitched. When i increase rpm's to 750+ it goes away and then when it returns it comes back again. Anyone have any idea what this may be?

 

alternator going bad already??? I think a few 04-08 guys had that issue...

 

I used to have a 99 ford some time back and had the same issue. I thought it was the alternator but it was actually one of my idler pulleys. I was able to track it down with some spray lube as I went from pulley to pulley until I found the one causing the noise.
Hopefully it is nothing more than that or the alternator.

 

Thanks guys i will check both out.

 

On my '08 w/5.4, I had a 'woot' or 'whistle' at idle when cold - this actually only happened below 35deg F.

There was a TSB for it - for an idler pulley replacement.

Doubt if your is the same issue being it's not cold now unless you are in the southern hemisphere.

 

I just been out ther eagain and messed around with it and it's 85f outside and it dont do it as soon as i start it but it starts a few secs after. It's very high pitched like one of them cat scare gadgets.

 

Then maybe listen closer to your A/C compressor - I know I can hear mine "grunt" for a second or two a few seconds after I start up.

Maybe try turning the climate control completely off while the truck is running, then kill the motor, and start it again - if it doesn't do it then I would think it is your A/C compressor.

 

I have turned the AC of whilst it's makeng the noise and noise still stays on. It dont sound like it's coming from the alternator but it's so hard to tell with how high pitched the sound is. I will try and get a closer listen the ac compressor

 

My point with the A/C was to try to eliminate something in the loop to help with diagnosis - sounds like it's not the compressor if the noise stays the same when you turn off the A/C.

 

My '04 does it and it's the belt, check that for tension or harmonic vibration?

 

this is not necessarily true, the compressor puts more of a load on the belt, tensioners and pulleys, the problem could still be a pulley even if the sound only happens when a/c is on.

did you try some lubricant on the pulleys? or a belt dressing with any results?

 

Any luck in locating the source of squeaking?

 

I'd let the dealer figure it out so they can't blame you and not cover the cost of the repair.

 

Well i have been busy the last few days and i aint had time to test it but so far it seems to have stopped but i aint left it running long enough to know.