When I first start my truck, the engine makes this horrible squeak. Can't really pinpoint where it's coming from in the engine. Once I get it past second gear while driving, the squeak completely stops. I've also noticed if I'm idling long enough after driving such as being in a drive thru for food, the squeak slightly comes back until I get going again and then it stops. Anyone ever experienced this? It's the 5.4 engine btw, forgot to include that.

 

Could be your serpentine belt tensioner or another accessory pulley that is trying to freeze up. Pull your belt and turn all the pulleys if you can. I would start there.

 

I'd start with checking the Sway bar and Radius arm bushings. Basically everything thats Rubber in the suspension.

 

Is it RPM dependent, speeds up if you rev the engine?

 

I miss read your post. I was thinking it was when you were driving over rough roads. My bad ..

 

Sorry for such a late reply, didn't realize my thread got more replies until now. Yes it is rpm dependent, does exactly what you said.

 

Serpentine belt is a great place to start. The noise I got from mine was the idler pulley in the top middle area of the engine. It was the easiest and cheapest and happened to be the problem with mine. Now is a good time to put a new serpentine belt on as well.

You can also get a can of belt dressing and spray the fan belt. This will stop the belt from slipping and can usually help with a squeak or squeal. But if you are using dressing, there is a good chance the belt is ready to be replaced.

 

Belts idlers and pulleys. Clean all pulleys with brass bristle wire brush before putting new belt on