Squeak from rear of truck

[ctrow89]

When I get in and out of my truck I often times hear a loud squeak coming from what I believe to be the rear of the truck. If I drive with my windows down I can also hear it when I'm going slower when it starts to shake. I don't hear it when I'm going faster, but I believe it's just the engine/exhaust that makes it impossible to hear. I've sprayed white lithium on every part of the suspension I could think of, but it still does it. I would have to say it's suspension because of the fact it does it when the truck shakes. I'm only a 180 lb guy so it's not exessive weight when I get in either. Anyone have any ideas or suggestions on what it might be or how to fix it?

[sinner6.0L]

Lube your tailgate pivots and latches on each side

Believe me, this ****ing drove me nuts when i first got my truck. I had no idea what it was for about a week